Patent ID: 7054553

Claim:
A monitoring apparatus for monitoring polarization-mode dispersion and chromatic dispersion of optical signals in wavelength division multiplexing (WDM) optical networks, the monitoring apparatus comprising: an optical distributor for distributing optical signals; a first light receiver for photoelectrically converting the optical signals to measure a frequency band of the optical signals distributed by said optical distributor; a second light receiver for photoelectrically converting the optical signals to measure an average power of the optical signals distributed by said optical distributor; a filter for passing output signals of said first light receiver over the frequency band of interest for measuring; a power meter for measuring signal power over the frequency band filtered by said filter; an analog-to-digital (A/D) converter for converting analog signals from said first and second receivers into digital signals; and a microprocessor for measuring average power of the optical signals by using the digital signals from said A/D converter and monitoring polarization-mode dispersion and chromatic dispersion using power values measured by said power meter; wherein said power meter produces a maximum power value (P(f) max ) and a minimum power value (P(f) min ) of the signals outputted from said first light receiver according to a polarization scrambling technique, said maximum and minimum power values being defined as: P(f) max ∝ cos(πcDL(f/f 0 ) 2 ) P(f) min ∝ [ cos 2 (πfΔτ)][ cos πcDL(f/f 0 ) 2 )] where c indicates a speed of light, D indicates a chromatic dispersion coefficient of an optical fiber in ps/km/nm, L indicates a length of the optical fiber, f indicates a frequency, and f 0 indicates an optical frequency of optical signals.