Optical alignment method and apparatus

An optical alignment apparatus for carrying out an optical alignment between an optical subassembly, comprising

• a laser diode for generating light, a focusing lens for focusing the light generated by the laser diode to an input end of an optical fiber, and
• a monitoring photodiode (mPD) for monitoring a state of light output power from the laser diode, and the optical fiber for a bidirectional optical transceiver module without an optical isolator, the optical aligning apparatus comprising:
• a first optical power meter for detecting power of the light outputted from the optical fiber;
• a current meter for detecting output current of the mPD;
• a relative intensity noise meter for measuring a RIN(Relative intensity noise) of the light outputted from the optical fiber;
• a controller for adjusting a position of the optical fiber such that the detected power has a maximum value, defocusing the optical fiber such that the detected RIN has a minimal value, obtaining, as a target value, a ratio of the detected output current at the maximum output power to the detected output current at the minimum RIN and controlling the optical alignment based on the target value;
• an optical alignment device for moving the optical fiber according to command of the controller;
• an optical splitter for mixing optical signals inputted from first and second terminals and splitting the mixed optical signals to third and fourth terminals or for mixing optical signals inputted from the third and fourth terminals and splitting the mixed optical signals to the first and second terminal, the first terminal being connected to an output end of the optical fiber;
• a variable optical reflector connected to the fourth terminal of the optical splitter to reflect the light back to the fourth terminal at a predetermined quantity of the reflection;
• and
• a second optical power meter connected to the second terminal of the optical splitter to measure power of the reflection reflected by the variable optical reflector and entering the optical subassembly.