BROAD-BAND TUNABLE ELECTROABSORPTION MODULATED LASER FOR WDM APPLICATION

Design and fabrication of the first 1.55-mu m wavelength turnable elec troabsorption modulated laser integrated with a bent waveguide distrib uted-feedback (DFB) laser is reported. A low-threshold high-efficiency and stable single-longitudinal-mode operation is obtained when the el ectrodes of the bent DFB waveguide were uniformly pumped. In a normal configuration where the modulator part is used as an intensity modulat or (i.e., AR coating an the modulator side and HR coating on the DFB s ide), stable single longitudinal mode output power close to 40 mW in f ree space is obtained with a 0-V bias to the modulator and an extincti on ratio of up to 15 dB, at 2.5 V. This single made stability is due t o the continuously distributed phase shift implemented ht the structur e thus reducing the photon pile-up inside the laser cavity as compared to apr abruptly quarter-wave phase-shifted DFB laser. With a nonunifo rm injection ire I-he multiple electrodes, it was possible to select o ne particular single longitudinal mode out of the three neighboring mo des inside the broad reflection band of the reflector. A wavelength tu ning range of about 3.5 nm was obtained while maintaining an optical o utput power of more than 2 dBm from each made. The device has a very l ow chirp (0.01-nm peak-to-peak) where modulated with a 2.5 Gb/s pseudo random binary sequence (PRBS) data stream and an error-free transmissi on over 200 km of non-DSF fiber has been demonstrated for all four wav elength channels separated by 100-GHz spacing. Also, when the modulato r part of the structure is used as a phase tuning element (i.e., antir eflectire (AR) coating on the DFB side and HR coating on the modulator side), me hare successfully demonstrated high-speed optical packet sw itching with a fast and wide tunable wavelength range. The optical pac kets can be modulated at 2.5 Gb/s and may be switched among four wavel ength channels in less than one bit period.