Electronic dispersion correction circuit for Plastic Optical Fiber channels

Large core, Step-Index Plastic Optical Fiber (SIPOF) is a cheap alternative to existing copper network interconnects. The low material, production and installation costs come at the price of large values of attenuation and intermodal dispersion for fibers reaching beyond 50 m. For a 150 m, 150 Mb/s link, the dispersion induced optical power penalty can be as large as 13 dB. Combined with a nominal attenuation of up to 0.22 dB/m, the signal drops under the sensitivity levels of current POF receivers. A non-intrusive solution to this problem could be receiver side electronic equalization. To ease integration with existing receivers and keep power consumption low, an analog implementation is proposed. As the optical channel does not behave like any low order electrical system, the design of an electrical filter with a fully matched response could result in a very complex system. Therefore, the performance of a general, low order, electrical filter was evaluated and compared with the theoretical case of full equalization in high level simulations. Based on these results, a 2 biquad adaptive gm-C filter was designed and implemented in a blind adaptive equalizer. The filter allows for individually tunable low and high frequency gain, enabling equalization of a 150 Mb/s link for fiber lengths ranging from 1 to 150 m.