Patent ID: 8867042

Claim:
A method for evaluating characteristics of an optical modulator containing a plurality of Mach-Zehnder interferometers (MZIs), wherein the optical modulator includes N (N is an integer 2 or more) MZIs connected in parallel, the MZI to be evaluated is a K-th MZI (MZI K ) and the strength of a n-th order side band component of the MZI K is defined to be S n,k , the method comprising: measuring output strength; and evaluating characteristics of the MZI, wherein the measuring output strength comprises determining the (S n,k ), the evaluating characteristics of the MZI further comprises: controlling a bias voltage applied to electrodes of the MZI K ; measuring the n-th order side band of the MZI K at a bias voltage minimizing the odd-order or maximizing the even-order component of side bands to obtain a first strength of the n-th order side band, and the n-th order side band of the MZI K at a bias voltage maximizing the odd-order or minimizing the even-order component of side bands to obtain a second strength of the n-th order side band, and determining characteristics of the MZI of the MZI K by using the first strength and the second strength of the n-th order side band.