LASER-DIODE MODULE WITH DISTRIBUTED-FEEDB ACK, SINGLE-MODE FIBER WAVE-GUIDE, AND OPTICAL ISOLATOR

The design of a module of a distributed-feedback laser diode is propos ed. The diode emits at the wavelength 1.55 mu m and is efficiently cou pled by a two-lens configuration to a single-mode fibre waveguide. The diode characteristics are stabilised by placing an optical isolator b etween the matching lenses. The isolator consists of two birefringent prisms and an yttrium iron garnet plate surrounded by an Nd-Fe-B ring magnet. The efficiency of coupling the diode radiation into the single -mode fibre exceeds 30% even after the isolator losses are taken into account. The measured degree of isolation produced by this device is a t least 35 dB. An experimental dependence of the relative intensity of noise I-RIN On the degree of backreflection was determined for a dist ributed-feedback laser diode matched to a Single-mode fibre. The inten sity I-RIN Of the investigated module was -140 dB/Hz.