Finite Impulse Response Filter Using 4-Port MMI Couplers for Residual Dispersion Compensation

Many implementations of optical finite impulse response filter for signal processing applications have been realized in integrated photonics using 2×2 couplers. We have implemented a filter using 4× 4 couplers. Such a filter is useful for the compensation of residual dispersion in a fiber optic transmission system. Silicon photonics realization using 4-port multimode interference couplers in 4 μm silicon-on-insulator technology has been carried out for a free spectral range of 100 GHz. The transmission and group delay for the fabricated device have been measured and a good agreement between the simulation and experimental results has been achieved. The proposed filter can compensate up to ±176 ps/nm of fiber chromatic dispersion.