Because of the low loss and low dispersion properties of silica optical fibers in the 1 pm wavelength region, optical fiber communication systems are expected to have a wide applications area. This paper describes recent development on InP/InGaAsP injection lasers as a light source for communication systems in the 1.2~1.6 μm wavelength region. Important factors for these lasers are 1)mode control, 2)temperature characteristics, 3)light output power, and 4)reliability. Transverse mode control is essential to assure linearity in light against current output characteristic and stable coupling efficiency into single mode fiber. Threshold current reduction is important for high temperature operation and assurance of long lifetime. Many types of index-guiding lasers have been developed to satisfy these conditions, and the transmission system at 400 Mbit/s with 25 km repeater spacing is going to be5installed in Japan. MTTF of a laser diode for this system is estimated to be about 10 hours in the condition of 5 mW at 50°C. Submarine systems require higher reliability of the device and the certification of longer life is now urgent. Single longitudinal mode lasers are desirable to realize next generation transmission systems of long haul and high capacity. For this purpose, distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers have been developed, and room temperature CW operations have been achieved.
H. Nagai, H. Nagai,
"Status of injection laser development in the 1.2~1.6 µm wavelength region", Proc. SPIE 0425, Single Mode Optical Fibers, (8 November 1983); doi: 10.1117/12.936223; https://doi.org/10.1117/12.936223