Patent ID: 6788397
Filing Date: 2004-09-07
Classification: G01M

Abstract:
A method of determining the modal power distribution (MPD) of an optical source launching a lightwave signal into a multimode fiber, the multimode fiber comprising a plurality of N degenerate mode groups and defined as including an input endface, an output endface and a predetermined length z, the modal power distribution defined as the optical power launched into each mode group n of the plurality of N degenerate mode groups, the method comprising the steps of:a) estimating responses hn(t) of each mode group to predetermined excitation pulses hsource(t); b) transmitting excitation pulses hsource(t) from an optical source through said multimode fiber, and measuring at the output endface of said multimode fiber a plurality of M mode-selective impulses responses hâ€²(i,t) defined as follows: hâ€²&af;(i,t)=&Sum;n&it;pn&af;(t)&it;pnselective&af;(i),where i &egr;{1, . . . , M}, n&egr;{1, . . . , N}, pn(t) is defined as the impulse response of mode group n, and pnselective(i) is defined as the fraction of power in mode group n under excitation by the source that is received in the ith mode-selective measurement; andc) determining the optical power pn launched into each mode group n of the plurality of N degenerate mode groups by setting pn(t)=pnhn(t) and solving the following equation for pn: hâ€²&af;(i,t)=&Sum;n&it;pn&it;hn&af;(t)&it;pnselective&af;(i).