A stable laser module with UV-curable resin for single-mode subscriber use

The successful development of a low-cost laser-to-fiber coupling module for single-mode subscriber use is reported. The module consists of a laser collimator and a fiber collimator with a microball lens in each collimator, that is, a two-microball-lens system in a confocal condition. The key technology of this module is the high-precision bonding of a microball lens in front of a laser diode using a recently developed ultraviolet (UV)-curable resin. An average coupling efficiency of -4.7 dB with a standard deviation as small as 0.37 dB is achieved. It is found that the resin has good bonding durability and the module is stable under a temperature cycle test of over 1400 cycles. Simple structure and high reproducibility of the module have reduced the cost. A monolithically integrated laser diode and photodiode (LD-PD) are also developed. An output efficiency as high as 0.03 W/A is achieved in a 10-60°C temperature range by combining the LD-PD with the module