Abstract: A channel transponder tests a circuit in a communication network. The channel transponder includes short reach receiver circuitry, long reach transmitter circuitry, long reach receiver circuitry, generator circuitry, short reach transmitter circuitry, and a connector. The short reach receiver circuitry receives a first short reach signal. The long reach transmitter circuitry transmits a first long reach signal based on the first short reach signal. The long reach receiver circuitry receives a second long reach signal. The generator circuitry generates a test signal. The short reach transmitter circuitry transmits a second short reach signal based on the second long reach signal and transmits the test signal from the generator circuitry to the circuit wherein the test signal is monitored over the circuit to determine performance of the circuit. The connector connects the generator circuitry to the short reach transmitter circuitry.

Abstract: A monitoring system is described that is comprised of a processing system and a database system. The database system is configured to store identities for a plurality of channels in the communication network. The processing system identifies an error on a first channel of the plurality of channels. The processing system identifies a second channel of the plurality of channels that is adjacent to the first channel based on the database system and determines if an error occurs on the second channel. The processing system identifies a third channel of the plurality of channels based on database system and determines if an error occurs on the third channel. The processing system identifies polarization-mode dispersion based on determining the error occurs on the second channel and determining the error does not occur on the third channel.

Abstract: A system identifies a polarization-mode dispersion (PMD) event in an optical fiber by determining error conditions in proximate wavelengths. The system includes an optical interface and a PMD identification system. The optical interface receives an optical signal from the optical fiber wherein the optical signal is wavelength division multiplexed with a plurality of wavelengths. The PMD identification system determines whether a first error condition exists in a first one of the wavelengths of the optical signal. The PMD identification system also determines whether a second error condition exists in a second one of the wavelengths of the optical signal wherein the second one of the wavelengths is proximate to the first one of the wavelengths. The PMD identification system also determines whether an acceptable condition exists in a third one of the wavelengths of the optical signal that is not proximate to the first one and the second one of the wavelengths of the optical signal.