Apparatus and method for modulating a laser beam and sensing the optical power thereof

摘要

A method and apparatus for modulating a beam from a laser with an electro-absorption modulator, and determining the optical power of the beam by measuring a back current produced by the electro-absorption modulator. The apparatus comprises an electro-absorption modulator and a back current detector. The electro-absorption modulator receives an electronic digital signal from an electro-absorption driver. The electro-absorption modulator modulates the beam of the laser according to the electronic digital signal. While modulating the beam, the electro-absorption modulator produces a back current. This back current is proportional to the optical power of the beam. The back current detector measures the back current to determine the optical power of the beam.

主权项

1. An apparatus for modulating a beam from a laser and determining an optical power of the beam during modulation, comprising:
an electro-absorption modulator for modulating the beam according to an electronic digital signal and generating a back current; an electro-absorption driver electrically connected to the electro-absorption modulator for generating the electronic digital signal; and a back current detector in electrical communication with the electro-absorption modulator, the back current detector for measuring the back current generated by the electro-absorption modulator, and flowing between the electro-absorption driver and the electro-absorption modulator, to determine the optical power of the beam, wherein the back current detector comprises:
a resistor electrically connected in series between the electro-absorption driver and the electro-absorption modulator;an analog difference amplifier electrically connected to the resistor for measuring a voltage difference across the resistor;two component groups, each component group attached to one side of the resistor and to the analog difference amplifier, each component group comprising a low-pass filter for filtering out the electronic digital signal; anda processor electrically connected to the analog difference amplifier for converting the measured voltage difference to an optical power using the value of the resistor and a transfer function.