Nonlinear Electronic Dispersion Compensator for Lasers

This paper presents the design of a 6 Gb/s transceiver with a nonlinearelectronic dispersion compensator (EDC) for a directly modulated distributed-feedback (DM-DFB) laser. At the laser output, a DM-DFB laser inducespower-dependent frequency chirp, which causes severe chromatic dispersion as well as pattern dependency on the received signal. Such time-varying nature of the dispersion increases the difficulty of compensation using conventional linear methods.

The proposed EDC overcomes the chirp-induced dispersion via a nonlinear equalizer at the receiver and a pattern-dependent pre-compensator at the transmitter. The EDC achieves an optical SNR gain of 14.69 dB at a BER of 1$ ,times {10^{ – 6}} $ in a 75 km SMF-28 fiber. The test chip is fabricated in a 90 nm CMOS process, and the EDC consumes 68 mW from a 1 V supply at 6$~$ Gb/s.