Overcome Challenges in Embedded Optical Interconnects Design

Gerald Persaud, V.P. Business Development
David Rolston, Ph.D., Chief Technology Officer

This article was also published by Electronic Design magazine. 

Introduction : Optical Technology in Embedded Design

The emergence of IoT in cloud computing and the demand for 4G and 5G networks worldwide are driving the increased use of optical transceivers in a wide variety of applications: business, government, industrial, academic, and cloud servers in public and private networks. Both local area networks (LAN) and wide area networks (WAN) are demanding more bandwidth packed into smaller spaces, and traditional copper interconnects cannot satisfy the insatiable appetite of all the network servers and gateway devices. Furthermore, the next generation of networking devices will need to be even more compact and faster. According to market research firm Radiant Insight, the optical transceiver market will reach $9.9 billion by 2020, three times its 2013 level.

Optical transceivers are the key components which transform electrical signals to light over optical cables. At the receiving end, another optical transceiver will convert the light back to electrical signals as shown in Figure 1. Most transceivers operate with speeds of 10, 40 and 100 Gbps. When higher speed is needed, multiple lanes are used in parallel to deliver the required bandwidth.

Demonstration of conversion of digital data and fiber optic light signals.

Figure 1: Demonstration of conversion of digital data and fiber optic light signals.

What are the Advantages Optical Networks?

Fiber optical networks or embedded communication systems have three key components: the optical transmitter, the fiber optical cable and the optical receiver. As described above, the transmitter converts electrical signals to light using either light-emitting diodes (LED) or laser diodes. At the receiving end, a photodetector is used to convert the light back to electrical signals. A transceiver combines the transmitter and receiver in one module.

The advantages of using fiber optics instead of copper include higher bandwidth, longer distance links, reduced weight, immunity to electromagnetic interference,and increased security.

Applications for Embedded Fiber Optics

Applications for embedded fiber optics are very broad and they often include projects that require very large bandwidth in confined areas, typically co-located with high-speed, high port count FPGAs or ASICs. Many of the civilian and military command and control monitoring systems (C4ISR), radar, FPGA interfaces, multiprocessor interconnects, CCD/CMOS imaging sensor arrays, high fidelity radar imagery, and systems requiring secure communications use fiber optics.

The block diagram of LightABLE LM module represents the typical functions of a transceiver

Figure 2: The block diagram of LightABLE™ LM SR4 module represents the typical functions of a transceiver

Challenges in Designing Embedded Systems with Optical Interconnects

There are three major challenges in designing embedded optical interconnects.

  • Creating an embedded system to support maximum bandwidth with the smallest possible footprint.
  • Designing or selecting the best optical interconnect able to perform in harsh environments with maximum MTBF.
  • Future-proofing the embedded system to maximize the return on system investment.

Balancing performance, space, power, and cost is a constant tradeoff and challenge. The design will depend largely on the bandwidth requirements of the embedded system, which can be a single boardcomputer (SBC) or multiple boards that fit in a chassis. Some of these network systems need to support many Gbps, thus the system design will also depend on the size and throughput of the interconnect. Multiple components may be needed which can increase the size of the SBC or chassis, and power and cooling requirements can also impact the overall system footprint. Many commercial grade optical interconnects operate in a limited temperate range, and cannot handle the shock and vibration of harsh environments, and some systems may need to operate in humid conditions. All these environmental factors will directly or indirectly affect the operational performance and life span of the products. In other words, a high-performance system will typically consume more power and require better cooling resulting in larger size and costing more. Therefore, tradeoff in system design is always an important consideration.

In Search of the Best Fiber Optic Interconnect Solutions

There are many considerations in selecting the best fiber optics interconnect solution, and they often require tradeoffs. The main considerations include investment protection, product performance, form factors, reliability, and integration considerations. The following provides guidelines in selecting or designing optimal embedded fiber optic interconnect solutions.

Standard-based solutions protect purchase investments

System performance is impacted by many factors, and there are a few rules of thumb to bear in mind:

  • The smallest form factor is desirable
  • Always choose rugged and reliable solutions even if they cost more
  • Guidelines for module integration and configuration should be observed

While there are many proprietary designs available, the best approach is to select VITA standard-based solutions because they are supported by a consortium along with a large ecosystem, so the design will be supported with upgrades over time. Additionally, the standard defines the technology and the connector specifications, which enables developers and integrators to select from multiple VITA-based vendors.

System performance is impacted by many factors

Fiber optics technology is capable of providing high-speed, low-latency, long distance communication with no electrical noise interference. However, many factors will impact the true, sustained performance and potential distance of the communication links. These factors include communication error rate, link budget, and receiver sensitivity. Additionally, when doing system design, it is important that full-duplex is part of the equation. Some new configurations can achieve up to 600 Gbps bandwidth, but there is overhead involved which may impact the actual throughput. For example, an unstable transceiver with high error rate will cause the system to perform retransmission which will decrease the overall system performance. The measure of this phenomenon is referred to as bit error rate (BER).

For fiber interconnect device or systems, the minimum BER should be 10-12. Higher performance can be achieved if BER is 10-15 or better. BER of 10-12 means that one error occurs every trillion transmissions. Additionally, a link budget greater than 13 dB with receiver sensitivity of -12dBm are recommended

600G LightCONEX LC plug-in module composed of two 24-lane transceiver side by side.

Figure 3: 600G LightCONEX plug-in module composed of two 24-lane transceiver side by side.

Smallest form factor is desirable

More and more embedded systems including single board computers (SBC) are using a smaller form factor. Therefore, it is important to select modules with the smallest footprint possible. Fiber optics transceiver modules can be as small as 1.3 cm × 1.3 cm (see Figure 4). Additionally, consider low profiles modules with a height of less than 5 mm. This will allow room for the SBC or systems to add additional functions on board.

150G and 300G LightCONEX Optical Transceivers

Figure 4: 150G and 300G LightCONEX Optical Transceivers

Always choose rugged and reliable solutions even when they cost more

Many fiber optics systems are used in harsh environments. As a result, commercial grade products will often fail or, at the minimum, have a shortened service life. It is important to choose solutions that will survive the environments of the target applications. Typical operating temperature should be from -40 °C to 100 °C or better with storage temperature from -57 °C to 125 °C. In addition, if the module consumes less power (100 mW per lane or better), it will create less heat and help achieve better MTBF. Other considerations should include shock and vibration resistance, passing MIL-STD-883 or better. The module should also be sealed to prevent corrosion due to exposure to moisture. As a rule of thumb, it is recommended that products pass the following tests to ensure the highest quality.

MIL-STD-883:

  • Vibration tests, Method 2007.3
  • Mechanical shock tests, Method 2002.4
  • Thermal shock tests, Method 1011.9
  • Thermal cycling tests, Method 1010.8

MIL-STD-202:

  • Damp heat tests, Method 103B MIL-STD-810:
  • Cold storage tests, Method 502.5

Rules for module integration and configuration should be observed

Illustration of a VPX blind mate connector comprising a 24 fiber MT ferrule and 10 RF coaxial connectors. The size of this connector meets VITA 66.4 standard.

Figure 5: Illustration of a VPX blind mate connector comprising a 24 fiber MT ferrule and 10 RF coaxial connectors. The size of this connector meets VITA 66.4 standard.

A well-designed transceiver should take into account the connector choice and location, as well as ease of system integration and configuration. As shown in Figure 5, an active blind mate optical design will make connector mating much easier and reduce the chances of making connection mistakes.

Additionally, there are two other rules to follow when considering connector selection or design. First, follow the VITA 66.5 “Optical Interconnect on VPX, Spring Loaded Contact on Backplane” standard which defines the connector dimensions. Then place the board-edge, plug-in module connector near the edge of the board, integrating an active parallel optic transceiver, and a spring-loaded backplane connector developed for VPX systems (part of the VITA standard) as shown in Figure 6. This approach will limit any additional cabling needed to bring the signals to the edge of the SBC board.

 LightCONEX Active Blind Mate VPX Optical Interconnect

Figure 6: LightCONEX Active Blind Mate VPX Optical Interconnect

The Embedded Interconnects Design Check List

The following paragraph can serve as a check list for ease-of-use.

  • Select solutions based on the VITA standard including VITA Section 6. This applies to the overall systems as well as the connectors.
  • For optimal system performance, select modules with low bit error rate (BER) such as 10-15.
  • Select small form factor modules in the range of 1.5 cm x 1.5 cm, with height profiles less than 5 mm. This will provide extra space for the circuit board.
  • Select rugged and reliable solutions that pass a minimum set of tests including the following:

MIL-STD-883:

  • Vibration tests, Method 2007.3
  • Mechanical shock tests, Method 2002.4
  • Thermal shock tests, Method 1011.9
  • Thermal cycling tests, Method 1010.8

MIL-STD-202:

  • Damp heat tests, Method 103B

MIL-STD-810:

  • Cold storage tests, Method 502.5

Select design/modules that are easy to integrate. These include blind-mate and broad-edge connectors.

Conclusions

The above article has outlined the advantages and challenges of using fiber optical interconnects. To use fiber optic cables, the electrical signals need to be converted to light signals using fiber optic transceivers. While there are many challenges to embedded fiber optics design, the benefits are substantial. The guidelines and design check list provided will help developers select the best solutions for their needs.

Optical Interconnect Design Challenges in Space

Guillaume Blanchette, Space Industry Manager, and
David Rolston, Ph.D., Chief Technology Officer, Reflex Photonics

Reprinted with permission from Aerospace & Defense Technology, September 2018.

Designers of fiber interconnect solutions have to consider space radiation attacks.

More and more aerospace applications are incorporating fiber optics technology into their designs due to its many advantages over copper. The thinner fiber solutions provide higher speed over a longer distance, are more reliable, offer higher noise immunity and, in many cases, lower the cost of ownership. Additionally, for the same diameter, fiber can pack more data than copper. Fiber is faster than the category 5 and 6 copper cables, approaching the speed of light (31% lower). For copper, pushing the speed beyond 1G is a challenge, but for fiber 10G is quite common. Copper is limited by distance. Usually, signal degradation with copper will occur after about 90 meters (2.7 km maximum for custom systems), while fiber can achieve more than 1.5 km without a problem and can deliver over 80 km depending on transmission signal quality.

Perhaps the most significant advantage of fiber is that it is not affected by electrical noise because the transmission uses light instead of electrical signals. The typical electromagnetic interference (EMI) that affects copper cables will not be encountered with fiber optics. Over time, the copper will also degrade and have worse signal-to-noise ratio
Compared with copper, a fiber system can be very efficient. In the case of a fiber-based Ethernet connection, more than 99.5% of the signal can be delivered to the Ethernet hub. Different types of convertors can be used to convert signals from the popular unshielded twisted pair (UTP) Ethernet connections over fiber cable, so many lower speed UTPs can be combined to achieve, for example, 100/120 Gigabits.

Challenges of Fiber Interconnect Design in Space

According to NASA, space radiation is made up of three kinds of radiation: particles trapped in the Earth’s magnetic field; particles shot into space during solar flares (solar particle events); and galactic cosmic rays, which are high-energy protons and heavy ions from outside our solar system (Figure 1). This adds up to ionizing radiation, proton and gamma ray attacks. These attacks have a major impact on electronic circuits, described as the total Ionizing Dose (TID) effects, which is measured in rad (radiation absorbed dose). Note that 1 rad = an absorbed energy of 0.01 J/kg of material, and 1 gray = 100 rads. The impact of exposure to space radiation ranges from degradation of performance to total malfunction. In space, one would imagine that the results can be quite serious.

The environment in space is harsh and demanding. Commercial-off-the-shelf (COTS) devices have to be able to endure the extreme temperature swings and the constant vibration. Failure is not an option in a space mission. Adding to this is the challenge to deliver maximum performance with minimum space, weight and power (SWaP), high mean-time-between-failure (MTBF), and reliability.

Designing for aeronautics is very different than designing for the earth environment. Aeronautical applications, such as spacecraft, satellites, and military aircraft are much more challenging. Designers of fiber interconnect solutions have to consider specific requirements to deal with those challenges. The three major challenges are:

  • Space radiation attacks
  • Operation in harsh environment
  • Achieving space, weight and power requirements (SWaP) and reliability
Spacecrafts experience constant attacks of space radiation from magnetic fields, solar flares and galactic cosmic rays.

Figure 1. Spacecrafts experience constant attacks of space radiation from magnetic fields, solar flares and galactic cosmic rays.

Best Practices for Optical Interconnect Design

paceABLE is a radiation-resistant optical transceiver created by Reflex Photonics. The modules measure less than 3 cm2 and weigh less than 15 g.

Figure 2. SpaceABLE SM is a radiation-resistant optical transceiver created by Reflex Photonics. The modules measure less than 3 cm2 and weigh less than 15 g.

Defend Against Radiation with Radiation-Resistant Design

What are the design considerations to meet the requirements as described above? It is important to defend against the radiation from ionizing, gamma, and other attacks. There are several methods to protect the device from radiation, including shielding, error correction, and using radiation-resistant components, which some refer to as radiation hardening. Shielding works for low-level radiation. Error correction works if the amount of radiation only temporarily impacts the device. However, heavy error correction will slow down the performance of the device.

Increasingly, more designs are incorporating radiation-resistant components to protect the device. Radiation-resistant silicon uses a different approach from the typical semiconductor wafers. The common approach is silicon on insulator (SOI) and silicon on sapphire (SOS), which enable radiation-resistant components to withstand an attack of ionizing radiation. While commercial-grade silicon can withstand between 50 and 100 gray (5 and 10 krad), radiation-resistant solutions can withstand 5 to 1000 times more depending on the types of components involved (Figure 2).

Design to Work in Harsh Environments and Follow Standardization

For the interconnect devices to survive in harsh environments, in addition to radiation resistance, they must include other parameters that may not be required for commercial-grade components. This includes meeting requirements for shock and vibration as specified in MIL-STD 883. It is strongly recommended that the devices be sealed from moisture and thermal shock within a wide range of operating temperature (typical -40°C to +100°C). Keep in mind that some devices may slow down when the temperature goes to the extreme, so it is important to measure sustained performance at those temperatures.

A different view of the SpaceABLE fiber-optic transceiver shows the connector for fiber-optic cable connection. At the bottom is the view of the ball grid array (BGA) for surface mount soldering.

Figure 3. A different view of the SpaceABLE SM fiber-optic transceiver shows the connector for fiber-optic cable connection. At the bottom is the view of the ball grid array (BGA) for surface mount soldering.

Designing or selecting open standard-based (VITA 66) interconnect devices ensures that the solutions will follow the lifespan of the standards and will not be easily obsoleted, as is often the case in proprietary or custom designs. To ensure that the devices meet minimum standards, they should meet – but are not limited to – the following industry standards:

  • MIL-STD-883, Method 2007.3 (vibration tests)
  • MIL-STD-883, Method 2002.4 (mechanical shock tests
  • MIL-STD-883, Method 1011.9 (thermal shock tests)
  • MIL-STD-202, Method 103B (damp heat tests)
  • MIL-STD-810, Method 502.5 (cold storage tests)
  • MIL-STD-883, Method 1010.8 (thermal cycling tests)
  • MIL-STD 883 (shock and vibration)
  • MIL-STD-883G, Method 1019.7 (total Ionizing Dose and Cobalt 60 gamma rays tests)
  • Total Non-Ionizing Dose (TNID) tests
  • Open VITA 66 standards
  • ECSS-Q-ST-60-15 Space Assurance

Achieving SWaP and Reliability

Weight becomes increasingly significant in space transportation and applications. The cost of sending 1 kg is estimated to be $50,000. Designing products to achieve optimal SWaP and high reliability with high MTBF is always the ultimate goal.

In space and military missions, failure cannot be tolerated. Satellites will be in orbit for many years, and repairing failed parts is not only difficult but also very costly. Therefore, designing for compact-size, ruggedness and high reliability will help developers stay competitive in the race to space. For example, the SpaceABLE interconnect solution with multiple lanes can yield as much as 150 Gbps. For reliability, a combination of sealing, ruggedness and radiation-resistant design plays into the longevity of the device. Its lifespan can range from a few years to over 20 years. The total cost of ownership including maintenance can be kept to a minimum with high-reliability devices.

Conclusions

Aeronautical applications face many design challenges that are unique to their intended environment. The best practices for optical interconnect design for space applications include the use of radiation-resistant technology to defend against space radiation, the use of components and devices that are designed to operate in harsh environments, and meeting SWaP and long-term reliability requirements. Finally, it is recommended to follow open standards like VPX and to look for solutions that comply with MIL and quality standards.

Optics all around: interview of Gerald Persaud

Amelia Dalton from EE Journal interviews Gerald Persaud, Reflex Photonics' V.P. Business Development.

This week we investigate embedded optical modules with Gerry Persaud from Reflex Photonics - The Light on Board Company. Gerry and I discuss the benefits of  their chip-sized embedded optical modules and why Reflex Photonics stands out in the optical module ecosystem. 

Gerald Persaud | V.P. Business Development

Gerald Persaud is responsible for overseeing global marketing, business development and customer initiatives related to the Reflex Photonic's product lines, as well as managing product development and customer technical support. 
[expand title="Read more" swaptitle="Close"]Gerald has over 20 years experience in telecom and defense. Prior to joining Reflex Photonics he held senior management roles in engineering and business development at Nortel, General Dynamic Canada, and Celestica. Gerald has developed many leading products in optical communication, wireless and advanced computing. Gerald doubled revenues at start-up Coresim in one year and precipitated an acquisition by Celestica. He also won the largest design contract ever in Celestica for an OTN switch.
Gerald holds a B.S. in Electrical Engineering at McMaster University.[/expand]

The Internet of space and radiation hardened transceivers

We are on the verge of a new era of human connectivity and communications – the Internet of Space (IoS) is upon us. The explosion of worldwide communications over the past 25 years has led to the pervasive use of mobile and land communications equipment with an abundance of platforms, applications and devices all driving the growth of many of the largest businesses in the world. There is no doubt that this trend will continue through the Internet of Things (IoT), along with improvements to the underlying network infrastructure. However, the next, ‘Small Step’ for man in terms of ubiquitous communications will be the ‘Giant Leap’ into the Internet of Space.

Internet of Space

The Internet of Space (IoS) is a long-term vision that leaders in some of the most technologically advanced companies in the world have begun to seriously consider. Both the European Space Agency and NASA have prepared plans that involve the deployment of networks of satellite around the Earth, Mars and the Sun. These networks are composed of complex communications networks for MIMO microwave antenna arrays and free-space line-of-sight laser links.
These technologies will be responsible for the communications of manned missions to Mars and will have to have the best in terms of redundancy, speed, and network management as most of what we send up, will never be fixed. Further to this however, will be the machine-learning A.I. systems on-board exploratory robots and landers for the moon and Mars including asteroid mining that will be tasked with resource extraction. For example, before the arrival of astronauts on Mars, dozens of intelligent, self-exploring robots and rovers will have to have found water on the planet for them. Basically, the self-driving cars of today will become the self-exploring robots of space.

New players in space exploration

OneWeb Satellites is planning the launch 900 satellites into low Earth orbit beginning in 2018, to deliver Internet access globally.

Coverage areas of each of OneWeb's planned satellites. (OneWeb)

The success of companies like SpaceX have shown that many of the traditionally held ideas about space exploration are breaking down and commercial opportunities are staring to be explored.
With more reliable, lower-consumption, smaller and more powerful computer systems, it is now possible to truly envision complex space networks.
OneWeb Satellites is planning the launch 900 satellites into low Earth orbit beginning in 2018, to deliver Internet access globally.

TeleSat, a Canadian company, has a plan to deploy almost 300 LEO satellites by 2021 to serve as an interconnect for continual 3G data networks for ship and aircraft connections over the oceans. However, as more commercial-off-the-shelf (COTS) parts are targeted for space applications as a mean to take advantage of powerful technologies at lower costs, a more meaningful business-case for vendors can now be made to support the space-vendor-ecosystem.

Space environment

However, there is a catch… The space environment itself is extremely severe; outside the protective cushion of the earth’s magnetosphere the exposure to radiation and extreme temperatures can destroy terrestrial electronics. Therefore, to really open these markets, the vendors will have to meet the space community half-way, and do what they can to “space-ify” their COTS products.

SpaceABLE radiation hardened optical transceivers

SpaceABLE is available in different configurations: 50G (4 TX plus 4 RX lane per device) and 150G (12 TX or 12 RX lane per device).

Reflex Photonics has a plan to do just that – with the cost of sending even just 1 kg into space at over $50 k, the advantages of using the Reflex Photonics’ line of small, lightweight, high-density SpaceABLE parallel optical transceiver modules inside the satellites will impact this enormously.
The Reflex family of SpaceABLE modules offer extremely high aggregate data rates (over 150 Gbps), the modules are less than 3 cm2 and weigh less than 5 g. They can be placed anywhere on a motherboard or linecard linking powerful CPU’s, GPU’s and FPGA’s across multiple boards and racks.

Rigorous testing

In terms of reliability, the SpaceABLE product follows the rigorous environmental testing of MIL-STD-883 with a variety of thermal shock, vibration, humidity and cycling tests included. Furthermore, Reflex Photonics has qualified these parts under very stringent radiation exposure tests: Active Heavy-Ion testing for latch-up, SEE and SET failures, long-term irradiation from PIF and NIF cyclotrons, and long-term exposure (over several weeks) of gamma-rays using Cobalt-60 on active parts. These tests were all done with reference to the ECSS-Q-ST-60-15 Space product assurance standard - Radiation hardness assurance - EEE components.
The space community is slowly evolving from an era of mega-projects and unlimited budgets to a dynamic industry that envisions a commercial market with volumes that can support multiple business. It can no longer afford the “nine-nines” of reliability – especially when private commercial enterprises like Virgin Galactic’s SpaceShipOne and XCOR’s Lynx space vehicles are rapidly closing in on tradition institutional domains. Reflex Photonics is part of this belief and this ultimate goal of Bringing space a little closer™ by offering optical transceivers and optical infrastructure that will enable the next generation of space exploration.

Reflex Photonics makes a splash at OFC

Reflex Photonics newly released optical transceivers for Embedded computing and Space captured much attention at OFC2018.

Visitors to Reflex’s booth were surprised by the small size of the LightCONEX active optical blind mate connector for rugged VPX computing and commented that this is the first solution to solve the many real-estate challenges for small rugged embedded computers.
As well, they thought the 300GBps bandwidth over 24 fiber optic channels offered great bandwidth and I/O density for next generation manned and unmanned vehicles.
The newly released SpaceABLE radiation hardened space transceivers from Reflex was also a big hit as engineers now have small chip sized optical transceivers that meets the needs for all future space equipment and high altitude aircraft.
Many visitors commented that Reflex is a leader in rugged optical transceivers and are happy we continue to focus on this market.

Demonstration of the LightCONEX blind mate optical interconnect at OFC
Demonstration of the LightCONEX blind mate optical interconnect at OFC
Sign up for Reflex Photonics' Newsletter

Sign up for Reflex Photonics' Newsletter

Reflex Photonics Newsletter Stay up to date and informed on new products and announcements with our newsletter.
The newsletter is published 6 times a year. (English only)

Your name (required)

Your Email (required)

Your Company

Sign me up for Reflex Photonics' Newsletter

By using this form you agree with the storage and handling of your data by this website. You may withdraw this consent at any time. Visit the Privacy Policy page to learn more.


What are LightCONEX active optical interconnects ?

Reflex Photonics announced the availability of the LightCONEX 12+12 Active Blind Mate Optical Interconnect solution for the embedded computing systems market. This new line of products features 12-lane full-duplex transceivers, each lane operating at up to 12.5 Gbps for an aggregate bandwidth of up to 300 Gbps. These transceivers are rugged, small-SWaP, low-cost modules, specifically designed for the VPX systems commonly deployed in defense and aerospace applications.

The LightCONEX Solution

The LightCONEX solution is the result of a close partnership between Reflex Photonics and Amphenol Aerospace Operations. The LightCONEX comprises a board-edge plug-in module connector, integrating an active parallel optic transceiver, and a spring-loaded backplane connector developed for VPX systems as shown in Figure 1.

Figure 1. LightCONEX Active Blind Mate VPX Optical Interconnect

The plug-in module connector reduces system cost and complexity since the optical transceiver mounts to the board edge via a low-height LGA connector. It requires no on-board optical cables handling or routing and frees up board space. The LightCONEX low profile plug-in module connector facilitates eventual integration of mezzanine card. This solution enables easy board card replacement for two-level maintenance and simplifies system upgrades.
The backplane connector, also part of the LightCONEX Solution, is “floating” to allow for precise alignment of the optical fibers from the mating MT ferrules. The spring-loading mechanism is coming from the attached fiber cable terminated by the MT ferrule ensuring optimal mating forces.

Figure 1.
LightCONEX Active Blind Mate VPX Optical Interconnect

The dimensions of these connector modules are defined to be fully compatible with the current VITA 66 standards and particularly the upcoming VITA 66.5 “Optical Interconnect on VPX, Spring Loaded Contact on Backplane” standard. The backplane connector is a drop-in replacement for the VITA 66.4 standard backplane connector.

The LightCONEX Active Optical Transceivers

The active optical modules used in the LightCONEX Solution are also available as standalone modules. They are offered in two versions, as shown in figure 2. The first version is offering a (4+4)-lane transceiver, a 12-lane transceiver or a 12- lane transmitter. The dimensions for each module of this version are 23 mm ×14 mm ×5 mm (L×W×H).

LightABLE LGA and LightABLE LGA 12+12

The second version is a (12+12)-lane full duplex transceiver. The MT ferrule of this module has 24 fibers in two rows of 12 on top of each other.
Its dimensions are only 32 mm × 14 mm × 5 mm (L×W×H).

Figure 2.
150G and 300G LightCONEX Optical Transceivers

The main features of these active modules are:

  • Rugged: MIL STD 883 compliant
  • Moisture resistant: sealed
  • Compact (L×W×H): 23 mm ×14 mm ×5 mm for the 12-lane version and 32 mm ×14 mm ×5 mm for the 24-lane version
  • High bandwidth: up to 12.5 Gbps/lane
  • Operating temperature: –40 ºC to 100 ºC
  • Reach: 300 m, OM3 fiber
  • Bit Error Rate: 10–15
  • Low power consumption: 1.4 W per module (12-lane), 2.8 W per module (24-lane)
  • Data interface: CML
  • Board mount: LGA connector

All modules include equalizers and pre-emphasis to compensate long traces; these features can be turned off for short traces (less than 10 cm) to reduce power consumption.

300G LightCONEX VPX Blind Mate Connectors

300G LightCONEX composed of a 12-lane transmitter plus a 12-lane receiver.

Figure 3a shows a 12-lane transmitter adjacent to a 12-lane receiver occupying the space reserved for RF coaxial connectors within the VITA 67.3 standard. This arrangement can sustain a total communication throughput of up to 300 Gbps.

300G LightCONEX VPX backplane connector.

Figure 3.
a) 300G LightCONEX composed of a 12-lane transmitter plus a 12-lane receiver.
b) 300G LightCONEX VPX backplane connector.

Future deployments

600G LightCONEX plug-in module composed of two 24-lane transceiver side by side.

To increase the I/O capability while maintaining a small size connector It is possible to set two 300G 24-lane transceivers side by side in the space reserved for RF Coaxial connectors following VITA 67.3 standard. Such a board is offering a total communication capability of up to 600Gbps! This version is illustrated in figure 4.

Figure 4.
600G LightCONEX plug-in module composed of two 24-lane transceiver side by side.

Illustration of a VPX blind mate connector comprising of a 24 fiber MT ferrule and 10 RF coaxial connectors.

Another configuration would use a combination of optical and RF coaxial connections on the same modules. Figure 5 (as proposed by TE Connectivity) illustrates such a configuration. In this illustration, a 300G 24-lane transmitter or receiver or transceiver is integrated with an array of 10 RF coaxial connectors.

Figure 5.
Illustration of a VPX blind mate connector comprising of a 24 fiber MT ferrule and 10 RF coaxial connectors. The size of this connector meets VITA 66.4 standard.

In summary

Optical Interconnects offer high bandwidth throughput, low latency, assure signal integrity and is the most scalable technology for fast upgrades. The rugged construction of the LightCONEX solution has demonstrated error free data transmission under severe shock, vibration, and temperature extremes.
The LightCONEX solution finds applications in multisensor systems, optical backplanes, routers, switches, and VPX systems, like those deployed in high-performance embedded computing systems for civilian and military command and control monitoring (C4ISR) systems.

Sign up for Reflex Photonics' Newsletter

Sign up for Reflex Photonics' Newsletter

Reflex Photonics Newsletter Stay up to date and informed on new products and announcements with our newsletter.
The newsletter is published 6 times a year. (English only)

Your name (required)

Your Email (required)

Your Company

Sign me up for Reflex Photonics' Newsletter

By using this form you agree with the storage and handling of your data by this website. You may withdraw this consent at any time. Visit the Privacy Policy page to learn more.


Taking the Fast Bridge between Neural Networks

Gerald Persaud, V.P. Business Development at Reflex Photonics gets interviewed by Embedded Systems Engineering

Read the whole interview here.

Gerald Persaud | V.P. Business Development

Gerald Persaud is responsible for overseeing global marketing, business development and customer initiatives related to the Reflex Photonic's product lines, as well as managing product development and customer technical support. 
[expand title="Read more" swaptitle="Close"]Gerald has over 20 years experience in telecom and defense. Prior to joining Reflex Photonics he held senior management roles in engineering and business development at Nortel, General Dynamic Canada, and Celestica. Gerald has developed many leading products in optical communication, wireless and advanced computing. Gerald doubled revenues at start-up Coresim in one year and precipitated an acquisition by Celestica. He also won the largest design contract ever in Celestica for an OTN switch.
Gerald holds a B.S. in Electrical Engineering at McMaster University.[/expand]

Mr Persaud was interviewed by Ms. Lynnette Reese, Editor-in-Chief, Embedded Systems Engineering
Here are the answers from Mr. persaud:

(...) Reflex Photonics provides tiny optical transceiver chips that can move a tremendous amount of data, which reduces the latency between GPUs so that they can appear as though working seamlessly, in parallel. (...) Technology for optical interconnects is vital in the industry, since processor speeds are outpacing copper wires for bandwidth and latency among devices, including VPX. During our recent interview, Gerald Persaud, VP Business Development at Reflex Photonics, told me this is a solvable problem, even in the harsh environments of military and outer space.

What is Reflex Photonics currently developing?

Today, we are focused on aerospace and defense, and industrial markets. Our expertise is delivering chip sized rugged high bandwidth optical transceivers that work in the harshest environments, such as space. For example, we were recently selected for a major satellite program because our parts could meet the required 20 years lifetime in space. Many optical transceiver suppliers claim high bandwidth operation at 25Gbps per channel but only for an operating temperature of 0 to 70ºC. All of Reflex Photonics’ rugged transceivers operate error-free over a temperature range of -50 to 100ºC while also meeting severe shock, vibration, damp heat, and thermal cycling requirements.

Reflex Photonics’ expertise is in ruggedized optical communications. How did your process for dealing with the challenges of harsh environments evolve?

In 2002 when we started the company our goal was to create a chip-size optical module that could be solder reflowed to support low-cost board assembly. This was much harder than we had imagined due to differences in material properties such as thermal expansion, thermal conductivity, and curing processes. Over the years we were able to incrementally improve our manufacturing processes from a commercial offering to a full space-qualified part. An excellent understanding of materials and processing is critical to the successful production of high-bandwidth rugged optical modules.

What is on your roadmap?

We plan to release higher channel speeds up to 56Gbps, more I/O density such as 24 transmitters or receivers in a chip size optical module. As well, we will continue to harden our parts to meet even wider temperature extremes of -65 to 125oC. Another product we recently released is active blind-mate optical connectors called LightCONEX®. We have gained a great deal of interest in this solution from the VPX community, as it frees up a lot of board space and simplifies field upgrades.

Can you give an example where Reflex Photonics has a play in VPX for machine learning?

One example of this is in unmanned vehicles where machine learning is critical for autonomous operation. Many sensors are interconnected to machine learning VPX compute farms via an optical switch. Optical interconnect, with its long reach, high bandwidth and light weight, is the only viable solution for advanced Autonomous Vehicles (AVs). From the start, Reflex set out to make the smallest rugged optical modules capable of supplying enormous bandwidth (BW) and optical channels. Today, Reflex Photonics’ rugged technologies are field proven and well positioned to take advantage of the trend for smarter, smaller, and robust systems.

How are you dealing with power challenges in a Small Form Factor (SFF)?

Power is indeed a challenge for mobile vehicles, which have a limited amount of power to supply onboard electronics. Today a 150Gbps chip consumes about 1.3 W. However, as bandwidth demand grows from 150Gbps to 2400Gbps over the next five to 10 years we cannot scale power linearly or the same chip will consume 21 W. And there are multiple chips per board!  We will need to introduce techniques to improve optical coupling efficiency and lower laser bias currents. As well, laser drivers and amplifier will need to operate at lower voltages. Closer integration of the drive electronics with optical transceivers could save a lot of power as the need for Clock and Data Recovery (CDR), equalizer, or pre-emphasis could be eliminated.

What are your competitors doing? How is Reflex Photonics any different?

Everyone including Reflex is racing to increase BW and interconnect density. However, in the aerospace and defense sector, suppliers must also meet the challenges of operating in a very harsh environment while keeping space, weight, and power [SWaP] to a minimum. Reflex is different in that we were the first to deliver a 150Gbps chip-size optical module that could operate from -50 to 100ºC while consuming 1.2 W. Most recently Reflex launched the first radiation-hardened parallel optical chip for space applications. These chips passed extreme environmental test conditions that our competitors were unable to meet. This is excellent news for the space industry, where size and weight are critical and smallsats are expected to do far more than their predecessors.

I have always considered price to be a specification. How is your pricing affected by ultra-hardening for space?

The price differential is not as significant as most would expect. In the old days when you said “space,” it meant 10 times the price. Those days are gone. There might be 30% increase in price for space grade over a military grade device. One grade down from military is the industrial device, which has similar operating temperatures but is not expected to have as long a life as Space and MIL grade parts.

Can you detail some of the challenges for optics at extreme operating temperatures?

Optical transceivers require exact alignment (less than five micrometers) of the laser or photodetector to the optical coupler. One challenge is maintaining this alignment over a wide temperature range. Reflex developed a patented approach using materials with low coefficient of thermal expansion and a simple coupling structure with no intermediate lens to maintain alignment over a wide temperature range of -57 to 125ºC. Another challenge is having a cost-effective sealing method (for moisture resistance in the optical path) that will withstand many thermal cycles without compromising the mechanical integrity of the module. Of course, there are other challenges like radiation hardening, solder reflow temperature survival, low power, optical sensitivity, and signal integrity.

What are the different grades of products that you have for harsh environments?

Most of our sales are for MIL, Space and Industrial grade parts. We offer some commercial grades such as QSFP and CFP for Telecom/Datacom markets. Our industrial components are used in many applications such as commercial aircraft, semiconductor wafer inspection, and instrumentation and tests. Most recently, we have had a number of automotive applications for our industrial parts.

Where would the automotive or transportation industry need rugged optical transceivers?

The automotive industry is quite large and includes cars, city buses, transport trucks, and other vehicles. We expect as self-driving or assisted driving goes mainstream fiber-optics will interconnect all systems in the vehicle. Compact AI engines will connect many sensors to automate driving. The vehicles of tomorrow will provide great energy efficiencies, less pollution, and a comfortable and productive driving experience. NVidia is now offering small form factor AI engines that are already deployed in Unmanned Aerial Vehicles.

Any optical transceiver is still going to need fiber to transport the signal in a system. Isn’t vibration a real problem for this kind of signaling in a vehicle?

No. Our parts have been tested to MIL-STD-883, Method 2007.3 for vibration and Method 2002.4 for shock. Vibration is 20 to 2000Hz, 20g, 16 minutes per axis and shock is 500g, 0.5ms pulse, 5 repetitions, 6 directions. These tests were done while transmitting and receiving 150Gbps with no errors.

That’s impressive. What distance and latency are we talking about?

Distance in AVs are typically less than 100 m, and latency is less than 1 microsecond.

Do you see Reflex Photonics involved in Autonomous Vehicles (AVs) someday?

Yes, AVs will require fiber-optics for security, bandwidth, latency, and SWaP. As the leading provider of rugged high bandwidth optical transceivers, Reflex is well positioned to deliver the most reliable optical interconnect for AVs. For large AV industries like commercial automotive one big challenge will be reducing the price of optical transceivers while keeping all the ruggedization testing in place. This will happen over a number of years, and so we will invest accordingly to track market prices.

When do you think AVs will start to get traction?

When the technology is considered safe adoption will happen. This will require years of education and trials. One area of concern is cybersecurity—nobody wants a hacker taking over their vehicle at 60 miles per hour. An effective strategy will be needed to isolate critical control functions from infotainment. This separation is done in commercial aircraft and similar standards will be imposed on AVs. Fiber-optics provide the first level of defense since they are immune to electromagnetic interference and therefore harder to disrupt. As well, learning machines will be smart enough to initiate automatic protection from dangerous threats. Protection techniques commonly used by military aircraft could be deployed.

How do you think the Autonomous Vehicle is going to play out, in reality?

The benefits of autonomous vehicles have long been known, but safety has always been a barrier. The recent advances in AI and low-cost sensors has generated great hope for convenient, safe and cost-effective people transport. Like everyone, I see a gradual shift to AV starting with assisted driving available now to special lanes for AV followed by AV completely dominating the roads. I see China embracing this technology to solve local pollution issues while seizing the opportunity to lead the automotive industry.

Sign up for Reflex Photonics' Newsletter

Sign up for Reflex Photonics' Newsletter

Reflex Photonics Newsletter Stay up to date and informed on new products and announcements with our newsletter.
The newsletter is published 6 times a year. (English only)

Your name (required)

Your Email (required)

Your Company

Sign me up for Reflex Photonics' Newsletter

By using this form you agree with the storage and handling of your data by this website. You may withdraw this consent at any time. Visit the Privacy Policy page to learn more.


LightCONEX makes an impact at VSO meeting

Reflex Photonics presented its updated LightCONEX at the January VSO meeting in Austin. The LightCONEX attracted a lot of attention and the presentation sparked a lot of questions from attendees.
The VSO meets every two months to discuss, plan, and develop standards to support its members' interests.

Demonstration of the LightCONEX blind mate optical interconnect at VSO
Demonstration of the LightCONEX blind mate optical interconnect at VSO
Sign up for Reflex Photonics' Newsletter

Sign up for Reflex Photonics' Newsletter

Reflex Photonics Newsletter Stay up to date and informed on new products and announcements with our newsletter.
The newsletter is published 6 times a year. (English only)

Your name (required)

Your Email (required)

Your Company

Sign me up for Reflex Photonics' Newsletter

By using this form you agree with the storage and handling of your data by this website. You may withdraw this consent at any time. Visit the Privacy Policy page to learn more.


Vision System Design talks about Reflex products

Vision System Design magazine  discusses some new products recently launched by Reflex Photonics.

Reflex Photonics, a Canadian company that develops embedded optical transceiver modules, has expanded into industrial and high-end space applications with the release of two new product lines.

LightVISION industrial optical modules (pictured) are screw-in, RoHS generic parts that can have a variety of optical interfaces, including the LightSNAP, which adds a standard MPO pluggable optical interface to the module. This, according to the company, offers a standard MPO cable connection with a board-mounted optical engine. LightVISION modules target applications such as machine vision, automotive, Industry 4.0, and high-resolution or high-speed cameras.

Reflex Photonics also announced the release of its SpaceABLE embedded optical modules, which are rugged devices engineered to withstand radiation doses as per the European Cooperation for Space Standardization ECSS-Q-ST-60-15C, while offering bandwidth greater than 150 Gbps in a chip-size package.

Read the whole article  here.

Sign up for Reflex Photonics' Newsletter

Sign up for Reflex Photonics' Newsletter

Reflex Photonics Newsletter Stay up to date and informed on new products and announcements with our newsletter.
The newsletter is published 6 times a year. (English only)

Your name (required)

Your Email (required)

Your Company

Sign me up for Reflex Photonics' Newsletter

By using this form you agree with the storage and handling of your data by this website. You may withdraw this consent at any time. Visit the Privacy Policy page to learn more.