An acoustic emission wave detector includes a housing, an optical fiber that guides light from a wideband light source into the housing, and an FBG housed in the housing and having a diffractive grating that reflects light guided into the housing. The FBG is fixed on a side of the other end in the housing such that the light guided into the housing is received by one end thereof. An acoustic emission wave from a high-voltage apparatus is received by the other end thereof.

Examples described herein relate to a method for synchronizing a wavelength of light in an optical device. In some examples, a heater voltage may be predicted for a heater disposed adjacent to the optical device in a photonic chip. The predicted heater voltage may be applied to the heater to cause a change in the wavelength of the light inside the optical device. In response to applying the heater voltage, an optical power inside the optical device may be measured. Further, a check may be performed to determine whether the measured optical power is a peak optical power. If it is determined that measured optical power is the peak optical power, the application of the predicted heater voltage to the heater may be continued.

An apparatus for estimating channel spacing, an apparatus for monitoring wavelength and a receiver where the apparatus for estimating channel spacing includes: a measuring unit configured to measure a spectrum gap width according to spectrum information of a received signal; and a determining unit configured to determine channel spacing by using the spectrum gap width according to a predefined corresponding relationship between channel spacing and spectrum gap width. And in this application, the measuring unit may determine reference power according to a predefined reference power level, and take a frequency difference between two frequency points in a left or right gap of a central channel in the spectrum information of the received signal corresponding to the reference power as the spectrum gap width. With this application, accuracy of wavelength monitoring may be improved.

Systems and techniques for mitigating spectral excursions in a passive optical network (PON) are described herein. A spectral excursion may be determined in the PON. The spectral excursion may indicate a laser transmission output on the PON at a wavelength that is outside a designated wavelength range. A duration may be identified for the spectral excursion. A first preamble offset may be generated using the duration of the spectral excursion. A round trip delay for the PON and a local time of day may be determined. The first preamble offset, the round trip delay, and the local time of day may be transmitted to an optical line terminal (OLT).

A network control apparatus includes a processor. The processor calculates a first OSNR corresponding to an allowable limit BER from an OSNR yield strength curve of a transmission end in a node of a transmission end. The processor acquires a reception BER of a second node of a reception end, and calculates a second OSNR corresponding to the reception BER from the OSNR yield strength curve of the transmission end. The processor calculates a first noise intensity corresponding to the allowable limit BER from the first OSNR. The processor calculates a second noise intensity corresponding to the reception BER from the second OSNR. The processor calculates a noise intensity margin, based on the first noise intensity and the second noise intensity.

An avionics unit for an avionics network is disclosed having a light emitter to provide a modulated broadband optical signal. The avionics unit also includes a first optical interface and a second optical interface. The first optical interface is optically connected to the light emitter and is to receive a removable wavelength selective filter to extract a modulated narrowband optical signal from the modulated broadband optical signal. The second optical interface is optically connected to the first optical interface and is to output the modulated narrowband optical signal.

Example embodiments of the present invention relate to optical wavelength directing devices used to construct compact optical nodes.

An optical network system includes an optical line terminal, an optical splitter that is connected to the optical line terminal via one first optical fiber, and a plurality of optical network units that are connected to the optical splitter via respective second optical fibers. The plurality of optical network units communicate with the optical line terminal using an optical signal of a working wavelength uniquely assigned to each of them. The optical line terminal communicates with an optical network unit that is connected to the optical splitter using an optical signal of a working wavelength and an optical signal of a spare wavelength that is common to a plurality of optical networks.

A wavelength-tunable optical filter control apparatus in an optical access system that uses wavelength-multiplexed optical signal of a plurality of wavelength channels includes a wavelength-tunable optical filter configured to pass an optical signal of a specific wavelength channel among the plurality of wavelength channels; a light receiving element configured to convert the optical signal that has passed through the wavelength-tunable optical filter into an electrical signal; a signal quality determining unit configured to determine a quality of the electrical signal; and a wavelength-tunable optical filter control unit configured to acquire a light intensity of the electrical signal and control a wavelength of the wavelength-tunable optical filter based on the acquired light intensity and a determination result of the quality of the electrical signal.

A method and apparatus for correcting inter-channel power imbalance and a receiver, applicable to a receiver in a multicarrier optical communication system, where the method includes: receiving by the receiver reference information transmitted by a neighboring receiver; and performing power imbalance error correction by the receiver according to the reference information. With this application, based on performing signal processing in the receiver, estimation errors produced due to power imbalance in the central channel and the neighboring channel may be reduced.