Novel gain measurement method without optical fiber alignment in a semiconductor optical amplifier

A novel chip gain measurement method for semiconductor optical amplifiers is proposed. By introducing the concept of a virtual optical source, the method eliminates the need for troublesome fiber alignment. The chip gain is obtained from the ratio of the optical filtered amplified spontaneous emission power to the virtual input one. We clarified the validity of the method theoretically, and successfully demonstrated gain measurement, comparing it with the conventional method with fine fiber alignment. The results agree well. The polarization dependence of the gain can also be estimated well by inserting a polarizer.