Tunable DFB Laser Array Integrated With Mach–Zehnder Modulators for 44.6 Gb/s DQPSK Transmitter

A tunable distributed feedback (DFB) laser array integrated with Mach–Zehnder modulators (TLA-MZMs) for a 44.6 Gb/s differential quadrature phase shift keying (DQPSK) transmitter has been developed. The TLA-MZMs covers 98 wavelength channels with the 50 GHz ITU-T grid in the $L$ -band. The side-mode suppression ratio for all channels was over 47 dB. DC extinction ratios over 25 dB were achieved for the MZMs. Our design achieves both the low modulation voltage (2 V $_{\pi}$) less than 3 V $_{\rm pp}$ and the low-excess loss less than 1 dB. 44.6 Gb/s DQPSK modulation with a low driving voltage of 3 V was successfully demonstrated.