Patent ID: 9640943
Date: 2017-05-02
CPC Classifications: H01S,H04B,H04J,H04Q

Claim:
1. An apparatus comprising: a Fabry-Perot (FP) laser diode; a Faraday rotator (FR) coupled to receive an optical output of the FP laser diode and that rotates a polarization of the optical output by substantially 45 degrees; an external modulator (EM) positioned between the FP laser diode and the Faraday rotator and coupled to receive an optical output of the FP laser diode and to modulate the optical output of the FP laser diode so as to produce a modulated signal; an optical fiber coupled at a first end to receive an optical output of the FR; a wave division multiplexer (WDM) filter coupled to a second end of the optical fiber to receive an optical output from the optical fiber; and a Faraday rotator mirror (FRM) coupled directly or indirectly to an output of the WDM filter, wherein an optical output of the WDM filter is partially reflected by the FRM such that the polarization of a reflected beam is rotated by substantially 90 degrees after transmission through and reflection by the FRM, and wherein the reflected optical signal then passes through the WDM filter, the optical fiber and passes through the FR with its polarization being rotated by the FR by substantially another 45 degrees before it is injected back into the FP laser diode.