Patent ID: 6993459
Filing Date: 2006-01-31
Classification: H04B

Abstract:
1. A method of calculating an extinction ratio of a laser, the method comprising: applying a sequence of data protocol signals, each having a header section and a data section, to the laser for exciting the laser, with the header section having at least first and second sub-sections, the first sub-section having a first predetermined bit pattern, and the second sub-section having a second predetermined bit pattern which is different than the first predetermined bit pattern, the laser outputting a sequence of optical signals, each having bit patterns corresponding to the first and second predetermined bit patterns of a corresponding sequence of data protocol signals; converting the sequence of optical signals to a sequence of electrical signals; low-pass filtering the sequence of electrical signals to pass a sequence of analog signals, each having a HIGH portion corresponding to filtering the first predetermined bit pattern in the first sub-section of the header, and having a LOW portion corresponding to filtering the second predetermined bit pattern in the second sub-section of the header; converting the sequence of analog signals to a sequence of digital signals; convolving the sequence of digital signals with a reference digital signal to generate a convolved signal; finding a peak of the convolved signal corresponding to an alignment between the first and second sub-sections and the reference digital signal; measuring the digital signal at the first and second sub-sections based on the alignment; and calculating an extinction ratio based on the measured digital signal at the first and second sub-sections.