A novel optical fiber transceiver offering 24 lanes at up to 10.3125 Gbps is presented; its external dimensions are 32.3 mm ×13.4 mm × 4.5 mm; it is compatible with the VITA66.4 standard or can be embedded on a host PCB; its operating temperature range is –40°C to 100°C.
By: Gabriel Monette, Saïd El Kharraz, and Jocelyn Lauzon. Reflex Photonics
Reflex Photonics technology brand. has developed compact 120G full duplex (12+12) 10.3125 Gbps/lane optical fiber transceivers for harsh environment applications such as Aerospace and Defense. These devices are designed to be embedded on printed circuit-boards in close proximity to high speed electronics in high performance embedded computing systems to optimize their performance. The same transceivers can also be integrated in board-edge connectors to free-up more space on the board and avoid optical fiber management. The active blind-mate optical connector interface associated to the board-edge mount application is based on the OpenVPX™ standards. These standards define interfaces between plug-in modules, backplane modules and chassis for products intended to be deployed in harsh environments.
These devices have been designed to maximize size, weight, and power (SWaP), being very compact, having a weight of 4.8 g and a power consumption around 120 mW/lane. Thermal management is optimized through multiple heat dissipation paths on the compact volume of these transceivers.
Define interfaces between plug-in modules and chassis for harsh environment applications.
Example of card layout for VITA 66.4.
The figure below shows the final configuration of the transceiver for both printed-circuit board embedded and board-edge mount application configurations. The embedded configuration is associated to Reflex's MicroClip™ technology that has proven its reliability in live vibration tests up to 41.7 grms and live fiber pull tests over 1 kg.
LightABLE LL used as a onboard embedded module.
Proprietary MicroClip™ MT ferrule
LightABLE being subjected to vibration test
LightABLE being subjected to live fiber pull test
LightABLE LGA Interposers come in two sizes: 1 mm and 3 mm.
LightABLE LL with 1 mm and 3 mm LGA interposers.
Transceivers are secured with screws with 1 to 2 in.-oz torque values
(0.7 N-cm to 1.4 N-cm).
The board-edge mount configuration was made to be compatible with VITA 66.4 optical interconnect on VPX base standard with a drop-in adaptor. Both configurations are associated to LGA (land grid array) sockets. A technology that has proven to be the perfect compromise for the electrical interface to offer high-speed performance, height flexibility, screw-in mechanical reliability and practical insertion/removal capabilities. The LGA contacts have a pitch of 1 mm. Although heat dissipation through these pins is limited, the periphery of the LGA sockets does offer a good thermal path to the host board that can be designed to dissipate heat.
The figure below shows the dimensions of these 12TRX transceivers compared with 4TRX transceivers, both including integrated microcontrollers. The height is comparable and the size (area or footprint) is about 1.5 times larger, for three times the communication capacity. Its weight is only about 25% larger than for the 4TRX. The optical interface for the 12TRX has a second row of optical fiber lanes on the same MT ferrule format. In order to make this design compatible with standard manufacturing technologies, we had to develop new optical alignment methods and rely on high precision automatic die bonding equipment.
Main technical challenges: tolerance on components and assembly precision
Active alignement. Optical loopback with RSSI access through microcontroller
Passive alignment under trial (5 µm precision needed)
Power supply filtering: 3.2 V to 3.4 V, with π filtering circuit (low pass filter).
With all lanes active: worst case
RX: −10 dBm sensitivity at 10-12 BER. To be optimized
TX eye with all lanes active
TX eye with no other lanes active
The performances of the 12TRX transceivers are as follows: sensitivity per lane better than -10 dBm for a BER of 10−12 from −40°C to 85°C with all lanes active.
We are currently improving on the settings and build to operate up to 100 ºC and maintain −12 dBm sensitivity across all lanes. We believe this design offers the best “performance/ cost per lane” ratio in the industry, for the same proven rugged constructions associated to Reflex 4TRX products, that have been used for many years in harsh environment applications.
The environmental qualification effort that is planned for this new product includes:
DVT to be completed