An optical pulse test apparatus according to the present disclosure includes a light generation unit configured to generate an optical pulse for generating backscattered light beams in an optical fiber under test and generate first light having an optical frequency for amplifying backscattered light in an LP11 mode out of the backscattered light beams in two LP modes through stimulated Brillouin scattering, and second light having an optical frequency for attenuating backscattered light in an LP01 mode out of the backscattered light beams in the two LP modes through stimulated Brillouin scattering, a mode demultiplexing unit configured to input the optical pulse, the first light, and the second light generated by the light generation unit into the optical fiber under test in the LP01 mode and separate, out of the backscattered light beams generated by the optical pulse, the backscattered light in the LP11 mode, a local oscillation light generation unit configured to generate local oscillation light by which the backscattered light separated by the mode demultiplexing unit is heterodyne-detected, a light reception unit configured to multiplex the backscattered light in the LP11 mode separated by the mode demultiplexing unit and the local oscillation light generated by the local oscillation light generation unit and photoelectrically convert the multiplexed light into an electrical signal, and an arithmetic processing unit configured to calculate a time-intensity distribution of the electrical signal obtained by the light reception unit photoelectrically converting the backscattered light in the LP11 mode.

Systems and methods include a method for overcoming optical time domain reflectometry (OTDR) dead zone limitations by using a few-mode fiber (FMF). Optical pulses are transmitted by a transmitter of an OTDR system through a mode MUX/DEMUX into an FMF. Light signals directed by the FMF in a backward direction through the mode MUX/DEMUX are received by the OTDR system through N single-mode fiber (SMF) ports corresponding to N modes in the FMF. Light signals from N−1 dead-zone-free SMF ports are collected by the OTDR system. Losses are measured and faults are located in the FMF based at least on the light signals.

In some examples, an optical time-domain reflectometer (OTDR) device may include a laser source to emit a plurality of laser beams. Each laser beam may include a different pulse width. A control unit may analyze, for each laser beam, a backscattered signal from a device under test (DUT). The control unit may generate, for each backscattered signal, a trace along the DUT. Further, the control unit may generate, based on an analysis of each trace along the DUT, a combined trace that identifies optical events detected along the DUT.

There are provided methods and systems that enable the use of the backscattering pattern produced by an optical fiber in an OTDR trace as a signature (also referred to herein as the “RBS fingerprint”) to recognize an optical fiber. It was found that it may be difficult to obtain repeatable signatures as those are sensitive to the wavelength of the OTDR laser source and the temperature of the fiber. OTDR methods and systems that are adapted to compare the backscattering pattern in a more repeatable manner are therefore provided. Once the repeatability issue is overcome, such signature can be used for identification purposes and enable new applications.

A system for providing advanced characterization of an optical fiber span is based upon the use of a pair of optical time domain reflectometers (OTDRs), located at opposing end terminations of the span being characterized. Each OTDR performs standard reflectometry measurements and transmits the resulting OTDR trace to monitoring equipment in a typical manner. The pair of OTDR traces is thereafter combined in a particular manner (“stitched together”) to create an OTDR trace of the entire fiber span (essentially doubling the operational range of prior art OTDR measurement capabilities). The transmit portion of one OTDR may be paired with the receive portion of the other OTDR, with time-of-light measurements (or signal loss measurements) used to determine optical path length and/or optical signal loss of the span. Using a multi-wavelength light source in the paired transmit/receive arrangement allows for a characterization of chromatic dispersion of the span.

An optoelectronic chip includes optical inputs having different passbands, a photonic circuit to be tested, and an optical coupling device configured to couple said inputs to the photonic circuit to be tested.

In some examples, automatic OTDR-based testing may include determining, based on analysis of a signal that is received from a DUT that is to be monitored, whether the DUT is optically connected. Based on a determination that the DUT is optically connected, a measurement associated with the DUT may be performed.

A system and method for performing an in-service optical time domain reflectometry test, an in-service insertion loss test, and an in-service optical frequency domain reflectometry test using a same wavelength as the network communications for point-to-point or point-to-multipoint optical fiber networks while maintaining continuity of network communications are disclosed.

There is provided a method for measuring an optical power attenuation value of a multimode DUT. The method generally has, using an optical source, propagating test light along a multimode device link having a first multimode device, the multimode DUT and a second multimode device serially connected to one another; said propagating including inducing a preferential attenuation of high-order optical fiber modes of the test light along the first multimode device and along the second multimode device; using an optical power detector, detecting an optical signal resulting from the propagation of the test light along the multimode device link and transmitting an output signal based on the detected optical signal; and using a processor, determining the optical power attenuation value of the multimode DUT based on the output signal.

The disclosed systems and methods for characterizing an optical fiber in a dense wavelength division multiplexing (DWDM) optical link. The characterizing comprising: i) applying a power dither to data bearing optical signals propagating in the optical fiber, the power dither having a high-power level and a low-power level; ii) computing optical time-domain reflectometer (OTDR) traces corresponding to the high-power level and the low-power level of the power dither; iii) averaging the OTDR traces corresponding to the high-power level and the OTDR traces corresponding to the low-power level into average OTDR traces; computing a differential Stimulated Raman Scattering (SRS) gain from the OTDR traces; and iv) adjusting the average OTDR traces based on the differential SRS gain.