Multi-wavelength light sources based on InP photonic integrated circuits for WDM lightwave communication systems

The authors present a brief review of recent work on the integration of a multi-wavelength distributed feedback (DFB) laser array with a star coupler and optical amplifiers using photonic integrated circuit technology. They have demonstrated that photonic integration is useful for simplifying the coupling between laser arrays and single mode fibers. A finished chip has been packaged with a single mode fiber pigtail as an optical output, 50 Ω microstrip lines for DC and RF inputs and a thermoelectric cooler under the laser submount to maintain a constant temperature. With a packaged module, simultaneous fifteen wavelengths coupling into a single mode fiber has been achieved for the first time with a laser array. From the wavelength shifts, the temperature rises under simultaneous operation are estimated to be about 6-11°C, depending upon where each laser is located within the chip. The optical power can be boosted up by an erbium-doped fiber amplifier or an on-chip amplifier. The inherent splitting loss of the star coupler can be avoided by forming a wavelength multiplexer with two star couplers