A system for monitoring optical signal-to-noise ratio (OSNR) is provided. In some specific examples, the system may use a pilot tone power of a signal modulated with pilot tone to derive the pure signal power and the variance of the whole electric field to derive the total power (pure signal power plus amplified spontaneous emission (ASE) power of the signal). The ASE power can be obtained by subtracting the pure signal power from the total power (ASE+pure signal). Once the ASE power and the pure signal power are known, the OSNR can be calculated.

A test equipment module and method of communicating maintenance data in a cable system is disclosed. The module comprises a receiver, a measurement system, a pilot generator, and a signal encoder. The receiver receives downstream signals from a host communication network. The measurement system determines a maintenance parameter value associated with the downstream signals. The pilot generator generates a pilot within the downstream frequency band, and a signal encoder encodes the pilot with the maintenance parameter value. The pilot generator adds the encoded pilot to the downstream signals in the communication network, such that a cable modem in the network can receive the encoded pilot and generate a spectrum that includes the encoded pilot. A PNM server receives the spectrum from the cable modem and determines the maintenance parameter value from the spectrum.

An optical transmitter has an optical modulator with a Mach-Zehnder interferometer, a pilot signal generator configured to generate a pilot signal to be superimposed on a drive signal for driving the optical modulator or on a substrate bias voltage applied to the optical modulator, and a controller configured to detect a ratio between a pilot component and a direct current component contained in a light output from the optical modulator and control at least one of an amplitude of the drive signal and a level of the substrate bias voltage such that the ratio becomes a constant value.

A system monitors optical performance of an optical link within an optical network. The system includes an optical transmitter having an expanded-spectrum pilot-tone modulator for modulating an expanded-spectrum pilot tone onto a high-speed data signal to generate an expanded-spectrum optical signal and an optical receiver for receiving the expanded-spectrum optical signal and for detecting and decoding the expanded-spectrum pilot tone to enable monitoring of the optical performance of the optical link.

Embodiments of this application disclose an optical signal sending method, a pilot receiver, and a transmitter, and relate to the field of optical communication technologies. The method includes: modulating an optical signal in a first state of polarization to obtain a first pilot signal; modulating the optical signal in a second state of polarization to obtain a second pilot signal, where a phase of the first pilot signal is different from a phase of the second pilot signal; and outputting a modulated optical signal. According to this application, this may reduce interference of a pilot signal transferred to an optical signal of another wavelength due to Raman power transfer effect.

The disclosed methods, apparatus, and systems allow safe and easy deployment of amplifier products that exceed laser safe limits without the need for fiber testing and characterization or OTDR techniques. One example embodiment is a method for ensuring eye safety in an optical network. The example method includes detecting optical connectivity between an output of a transmit amplifier and a passive optical processing element. The transmit amplifier is located at a first network node and is configured to output optical power greater than eye-safe level. The passive optical processing element is located at a second network node and is configured to guarantee a reduction of a maximum optical power level at an output side of the passive optical processing element to an eye-safe optical level. The detecting occurs at the first network node, and the transmit amplifier is enabled or disabled as a function of detection of the optical connectivity.

A test equipment module and method of communicating maintenance data in a cable system is disclosed. The module comprises a receiver, a measurement system, a pilot generator, and a signal encoder. The receiver receives downstream signals from a host communication network. The measurement system determines a maintenance parameter value associated with the downstream signals. The pilot generator generates a pilot within the downstream frequency band, and a signal encoder encodes the pilot with the maintenance parameter value. The pilot generator adds the encoded pilot to the downstream signals in the communication network, such that a cable modem in the network can receive the encoded pilot and generate a spectrum that includes the encoded pilot. A PNM server receives the spectrum from the cable modem and determines the maintenance parameter value from the spectrum.

A method for conveying information through an optical fiber link between a transmitter and a receiver of an optical communication system. The method includes generating, by the transmitter, a predetermined spectral change, and inserting the predetermined spectral change into an optical fiber link for transmission to the receiver. A detector associated with the receiver detects the predetermined spectral change in an optical signal received through the optical fiber link, and generates a detection signal in accordance with the detection result. The detector is independent of a digital signal processor of the receiver that is configured to recover data modulated on the optical signal received through the optical fiber link.

The disclosure is directed to a method and system for generating a pilot tone for an optical signal with an optical telecommunications system. The pilot tone is generated in the digital domain by modulating the data to be transmitted to a destination node within the optical telecommunications network. The modulation of the data introduces occurrence modulation to the optical signal.

Systems and methods for performing wavelength conflict detection are provided. These are to detect situations in optical networks where two instances of the same wavelength channel have been added. Wavelength conflict detection is performed for each of a plurality of possible wavelength channels that could be present in an optical signal, each wavelength channel that is present modulated by a pilot tone signal with a respective pilot tone frequency, the pilot tone signal carrying M-ary pilot tone data, M=2.sup.n, n?1, with a respective one of M different sequences being used to represent each of M possible data values over a data value period. Conflict detection for each wavelength channel involves performing correlation peak detection using each of the M different sequences to determine correlation peaks for each of the M different sequences, and, based on the determined correlation peaks, determining whether multiple instances of the wavelength channel are present in the optical signal.