A measurement apparatus includes: a light source unit configured to generate optical signals of, from among n+1 frequencies (n is an integer of 3 or larger) at a predetermined frequency interval, n frequencies except for a target frequency, and output the generated optical signals to an optical transmission path that is a measurement target; an optical power measurement device configured to measure of an optical signal of the target frequency output from the optical transmission path and generated in the optical transmission path as a result of four-wave-mixing of the optical signals of the n frequencies; and a processor configured to determine a power spectrum density of non-linear interference noise that occurs in the optical transmission path, by multiplying the power of the optical signal of the target frequency by an adjustment value.

A fiber link system, method and device for masking signals on a fiber link system. The system includes sending a desired sequence of information in the form of a true signal that is typically intended to be transferred between legitimate users at both ends of a link. Sending chaff signals, or subterfuge signals, alongside the true signal to mask such legitimate signals in the fiber cable from intruders tapping into the fiber cable.

The present application provides an optical port auto-negotiation method, including: a: selecting a downstream to-be-received wavelength; b: listening to a downstream message on the selected downstream to-be-received wavelength, performing c if a wavelength idle message is received, and returning to a if no wavelength idle message is received within a specified or fixed time, where the wavelength idle message is used to identify that the wavelength is not occupied or not allocated; c: sending a wavelength application message on an upstream wavelength, performing d if a wavelength grant message is received in a downstream direction; otherwise, going back to a or b, where the wavelength application message is used to identify a request for allocation of the wavelength, and the wavelength grant message is used to identify acknowledgment of wavelength allocation; and d: setting an optical port auto-negotiation success flag bit. The present application further provides an optical module.

The present disclosure provides a method. The method comprises: Step S1: configuring a periodic excitation source to transmit a periodic excitation signal A; Step S2: sampling an output signal A+N.sub.A at an output point of the periodic excitation signal A with a sampling device AA, and averaging the output signal A+N.sub.A over one or more periods to filter noise; Step S3: inputting the sampled output signal A+N.sub.A as in input to a device or a channel H to be measured; Step S4: sampling an output signal B+N.sub.B at an output point of the device or the channel H to be measured with a sampling device BB, and averaging the output signal B+N.sub.B over one or more periods to filter noise; and Step S5: transmitting sampling results from the sampling device AA and the sampling device BB to an analysis software C to calculate a transfer function of the device or the channel H to be measured.

A coherent optical spectrum analyser for monitoring a spectrum of a fibre link is provided. The coherent optical spectrum analyser comprises an input connectable to the fibre link, the input being connected to a first input of a coherent detector having at least two input, the first and a second input, and an output. The coherent optical spectrum analyser further comprises a local oscillator having an output connected to the second input of the coherent detector, wherein the output of the coherent detector is connected to a first input of a processing unit, the processing unit also being connected to an input of the local oscillator, the processing unit being configured for analysing information from the coherent detector. The local oscillator comprises a semiconductor laser tuned by temperature to a specific wavelength and swept by changing a bias current, the local oscillator being controlled by the processing unit.

An integrated pluggable optical tap module configured to be coupled to a host interface of a network equipment for tapping a signal of an optical transport link comprises a first, a second optical interface, and an active optical receiver. The optical pluggable module also includes a passive optical tap for splitting a signal received from the first optical interface and transmitting the signal on the second optical interface and a copy of the signal to the active optical receiver. The active optical receiver converts said signal to an electrical signal for transmission to the host interface.

Power distribution modules in distributed antenna systems include fan monitoring circuits for indicating an alarm condition to head-end equipment. The alarm condition can be used by system operator/owners that a fan is drawing excessive power, thereby detracting from system performance, or indicating that the fan may fail. The alarm condition signal can be returned to the head-end equipment via an uplink communication path between a remote unit powered by the module and the head-end equipment.

Power distribution modules in distributed antenna systems include fan monitoring circuits for indicating an alarm condition to head-end equipment. The alarm condition can be used by system operator/owners that a fan is drawing excessive power, thereby detracting from system performance, or indicating that the fan may fail. The alarm condition signal can be returned to the head-end equipment via an uplink communication path between a remote unit powered by the module and the head-end equipment.

A cable signal detector for being provided at a connector at an end of a communication cable transmitting differential signals or at a relay connector to be connected to the connector to detect an existence of information communication. The cable signal detector includes an amplifier circuit that branches and extracts a portion of a signal transmitted through the communication cable, amplifies the extracted signal and outputs the amplified signal, and a display portion that display the existence of information communication based on the output of the amplifier circuit. The amplifier circuit is mounted on a detection device formed separately from the connector or the relay connector. The connector or the relay connector is configured to transmit the extracted signal to the detection device.

A cable signal detector for being provided at a connector at an end of a communication cable transmitting differential signals or at a relay connector to be connected to the connector to detect an existence of information communication. The cable signal detector includes an amplifier circuit that branches and extracts a portion of a signal transmitted through the communication cable, amplifies the extracted signal and outputs the amplified signal, and a display portion that display the existence of information communication based on the output of the amplifier circuit. The amplifier circuit is mounted on a detection device formed separately from the connector or the relay connector. The connector or the relay connector is configured to transmit the extracted signal to the detection device.