Integrated Wide-band Mach-Zehnder Interferometer for Wavelength Division Multiplexing (WDM) Networks

Abstract

Wavelength Division Multiplexing (WDM) is a very attractive option to satisfy the rapidly growing bandwidth needs. Multiplexing devices made it possible to exploit the real bandwidth of optical fibre. An optical switch is a key device while performing the reconfigurable multiplexing operations. Several number of wavelength switches have been demonstrated which are based on various approaches. Mach-Zehnder interferometer based structure is considered as efficient due to its characteristics, such as: low crosstalk, low insertion loss, and fabrication simplicity. We have designed an optimal two channels tuneable wavelength switch based on Mach- Zehnder interferometer (MZI). The material used for the fabrication of the device is a compressive strained multiple quantum well (MQW) grown to a silicon doped InP wafer. We have analysed the waveguide and multimode interference (MMI) coupler to be used in our device. Two MMI couplers of ~100 μm length and 4.5 μm of width have been used in our design due to their high bandwidth, low loss, and low crosstalk characteristics. A 400 μm long active phase-shifter is set in one of the two arms of MZI for the phase shift function as well as wavelength tuning. Wavelength tuning is obtained by injecting the DC biased current in the phase-shift region. The device analysis, on the basis of bandwidth and crosstalk, was performed by using Beam Propagation Method (BPM). A FWHM bandwidth of about 390 nm is achieved at the central wavelength 1550 nm. The transmission loss is recorded as low as 24 dB while a crosstalk of -38 dB has to be discovered in our solutions.