Decision feedback equalization for enhancing plastic optical fiber transmission in automotive optical ethernet

Abstract

With the rapid development of high-level road traffic system and the implementation of autonomous mobility system, smart driving has become an important work toward the realization of intelligent society. Large capacity of imaging data acquired by imaging sensors and large surrounding traffic information data are required to be transferred to vehicles via in-vehicle transmission lines. Plastic optical fiber (POF) has potential for this type of next generation automotive data networks due to its relatively high bandwidth compared to current coaxial cables, easy connection due to relatively large core diameter, low cost, and immunity to electromagnetic interference. However, due to fiber mode dispersion, the bandwidth of large core POF is limited to several hundred Mega-Hertz for a hundred-meter-long transmission line. Equalization (including linear equalization and feedback equalization) was proposed to be used for eliminating inter symbol interference introduced by the limited bandwidth of the POF. In the past, fiber transfer function was supposed to be a Gaussian shape in simulations, which is not the actual situation. In this work, we first calculate the POF transfer function based on the power flow equation and the real fiber parameters. Then, we evaluate the transmission quality of raised cosine pulse sequence by observing the eye-pattern at the receiving end, which shows clear eye closure. Next, we designed a decision feedback equalizer and applied it to improve the bit rate of the transmission line. The result showed that transmission quality is improved, but the speed cannot achieve Gbps by equalizer alone.