A DFB-LD module integrated with 60 dB optical isolator for coherent lightwave transmission systems

The coupling efficiency between the distributed feedback-laser diode (DFB-LD) chip is presented and the single-mode fiber is as high as -5.7 dB (27%) including the insertion loss of the isolator. The spectral linewidth measurement using the self-delayed heterodyne method shows 26 MHz under the condition of IF=I/sub th/+50 mA. No changes in the DFB-LD chip properties are observed after packaging. The comparison to another DFB-LD module with a 30-dB isolator confirms the immunity of the spectrum against -14-dB Fresnel reflection. The results show that the DFB-LD module is sufficiently stable to be applied to the coherent lightwave transmission systems.<
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