Techniques for maintaining equipment of a PON include determining a current optical profile for each segment of a plurality of segments of a PON, and detecting that the current optical profile of a particular segment is outside of a designated operating range. Based on the detection, drifts over time of the optical profile of the segment and of optical profiles of one or more other segments that share respective common endpoints with the segment are determined and compared, and based on the comparison, a component of the PON (e.g., an endpoint or an optical fiber) is identified as requiring maintenance. Each segment's optical profile corresponds to characteristics of optical signals delivered over the segment (e.g., attenuation, changes in frequencies, changes in power outputs, etc.), and current optical profiles of the PON's segments may be repeatedly updated over time to continuously monitor for components that need maintenance.

In some examples, high speed bidirectional OTDR-based testing may include transmitting data from a first end of a device under test (DUT) towards an optical time-domain reflectometer (OTDR) that is operatively connected to a second opposite end of the DUT. Further data that is transmitted by the OTDR may be received from the second opposite end of the DUT towards the first end of the DUT. Based on an amplitude of the further data, a direction of receiving of the further data may be adjusted towards a first receiver or towards a second receiver.

In some examples, an optical time-domain reflectometer (OTDR)-based high reflective event measurement system may include an OTDR, and an N by M optical switch optically connected to the OTDR or disposed within the OTDR. The optical switch may include a variable attenuator mode and at least one optical fiber connected to at least one output port of the optical switch. At least one fiber optic reflector may be disposed at an end of the at least one optical fiber. A variable optical attenuator may reduce, for the at least one optical fiber including the at least one fiber optic reflector, an amplitude of reflective peaks.

In some examples, an optical time-domain reflectometer (OTDR)-based high reflective event measurement system may include an OTDR, and an N by M optical switch optically connected to the OTDR or disposed within the OTDR. The optical switch may include a variable attenuator mode and at least one optical fiber connected to at least one output port of the optical switch. At least one fiber optic reflector may be disposed at an end of the at least one optical fiber. A variable optical attenuator may reduce, for the at least one optical fiber including the at least one fiber optic reflector, an amplitude of reflective peaks.

A loss-based wavelength meter includes a first photodiode configured to measure power of monochromatic light; and a loss section having a monotonic wavelength dependency, wherein a wavelength of the monochromatic light is determined based on measurements of the first photodiode after the monochromatic light has gone through the loss section. This provides a compact implementation that may be used in integrated optics devices using silicon photonics as well as other embodiments.

In some examples, high speed bidirectional OTDR-based testing may include transmitting data from a first end of a device under test (DUT) towards an optical time-domain reflectometer (OTDR) that is operatively connected to a second opposite end of the DUT. Further data that is transmitted by the OTDR may be received from the second opposite end of the DUT towards the first end of the DUT. Based on an amplitude of the further data, a direction of receiving of the further data may be adjusted towards a first receiver or towards a second receiver.

In order to reduce a delay at the time of detecting inputted optical signals in an optical receiver using a variable optical attenuator, the optical receiver includes: a variable optical attenuator that outputs optical signals by attenuating the intensity of inputted optical signals; a photoelectric converter that converts the optical signals into electric signals; an amplitude detection circuit that outputs an output voltage based on the amplitude of the electric signals; an optical attenuator control circuit that outputs signals for controlling an attenuation quantity of the variable optical attenuator based on the output voltage; a signal detection circuit that outputs signal detection output by comparing the output voltage and a signal detection threshold voltage, i.e., reference of signal detection, to each other; and a threshold control circuit, which monitors the output voltage, and which changes the signal detection threshold voltage when an output voltage change state becomes stable with time.

Techniques for improving redundancy in semiconductor-based optical communication systems are provided. For example, two or more semiconductor optical amplifiers (SOAs) may be provided in an optical repeater, and each SOA may form a respective amplification path. When failure occurs on a first SOA, a second SOA that is different from the first SOA can be selected. In one example, the selection may be based on wavelength division multiplexing (WDM), and in another example, the selection may be based on optical switching. The two or more SOAs (and other optical components) may be integrated in the same substrate package.

Techniques for maintaining equipment of a PON include determining a current optical profile for each segment of a plurality of segments of a PON, and detecting that the current optical profile of a particular segment is outside of a designated operating range. Based on the detection, drifts over time of the optical profile of the segment and of optical profiles of one or more other segments that share respective common endpoints with the segment are determined and compared, and based on the comparison, a component of the PON (e.g., an endpoint or an optical fiber) is identified as requiring maintenance. Each segment's optical profile corresponds to characteristics of optical signals delivered over the segment (e.g., attenuation, changes in frequencies, changes in power outputs, etc.), and current optical profiles of the PON's segments may be repeatedly updated over time to continuously monitor for components that need maintenance.

A transmission device configured to transmit main signal light to another transmission device through a transmission line, the transmission device includes a transceiver configured to output supervisory signal light including information on supervisory control on the transmission device and the other transmission device, an attenuator configured to attenuate the supervisory signal light, a combiner configured to combine the supervisory signal light to the main signal light, and a control circuit configured to control an attenuation amount of the attenuator so that power of the supervisory signal light received by the other transmission device approaches a given target value.