137 Gb/s PAM-4 Transmissions at 850 nm over 40 cm Optical Backplane with 25 G Devices with Improved Neural Network-Based Equalization

An improved neural network-based equalization method is proposed and experimentally demonstrated. The up-to-137 Gb/s transmission of four level pulse amplitude modulation (PAM-4) signals with 25 G class 850 nm optical devices is achieved over an in-house fabricated 40 cm optical backplane. An in-depth investigation is conducted regarding the impact of delayed taps and spans on equalization performance. A performance comparison of the proposed method with the traditional maximum likelihood sequence estimation (MLSE) and decision feedback equalization (DFE) is also undertaken. For the bit rate from 80 to 100 Gb/s, the proposed method achieves an adopted hard-decision forward error correction (HD-FEC) requirement at a received optical power (RoP) of −9 and −8 dBm, while DFE and MLSE cannot meet the HD-FEC requirement. When the bit rate increases from 120 to 137 Gb/s, the proposed equalization method still successfully maintains the acceptable system performance at an RoP of −4 and −2.5 dBm. Furthermore, the specific bit error rate (BER) performances for varied maximum achievable bit rate under different RoPs by applying MLSE and the proposed method are also analyzed. This provides an important potential solution to realize the future data centers.

Design and Development of a Fully Automated Assembly Solution for Optical Backplane Interconnection Circuits

The paper presents the design and development of a new robotized assembly system of optical backplanes in high-capacity ICT (Information and Communication Technology) apparatus, mainly used for switching stations and distribution networks. The optical backplane solution consists of several optical fiber ribbons positioned on a planar backplane according to an innovative and optimized full-mesh layout where the overall optical interconnection is partialized into a plurality of different independent sub-circuits. Each optical interconnection sub-circuit consists of optical fiber ribbons with standardized optical and mechanical interfaces and customized components that have to be carefully and precisely assembled in order to achieve connections with low optical power losses. The paper describes the method and the main devices and tools conceived for the automatic assembly of optical interconnection sub-circuits, highlighting the critical aspects and the proposed solutions towards the automatized assembly of the whole optical backplane.