A line monitoring system may include a laser source to launch a probe signal over a first bandwidth, a polarization maintaining tap to receive and split the probe signal, into a first portion and a second portion, a polarization rotator to receive the first portion and send the first portion to a transmission system, a return tap to receive the second portion and to receive a return signal from the transmission system, wherein the return signal being derived from the first portion, a photodetector coupled to receive an interference signal from the return tap, wherein the interference signal is generated by a mixing the return signal and the second portion, where the photodetector is arranged to output a power signal based upon the interference signal, and a power measurement system to measure the power signal at a given measurement frequency over a second bandwidth, comparable to the first bandwidth.

In this invention, a novel technique is introduced to measure chromatic dispersion (CD) in optical fibers. This technique is based on a relatively low-frequency optoelectronic oscillation (OEO) to provide fast, precise and low-cost method for CD measurement that can be implemented easily in commercial instruments. The proposed setup is implemented to measure the CD in normal single mode fibers with lengths of 40 km, 10 km, 1 km. Moreover, it is implemented to measure CD in 400 in of nonzero dispersion shifted fiber to test the system ability to resolve small chromatic delays. The proposed setup can resolve delays less than 0.1 ps/nm (which can be further improved by increasing the oscillation frequency) and measure CD with precision as low as 0.005 ps/nm.km as low as 20 seconds over a wavelength range from 1500 to 1630 nm. Further improvements may be possible by slightly better system design.

The output profile of light from a multimode optical fiber is determined using a geometrical optics approach where the rays launched into the fiber conform to LP-modes of the fiber. This output profile can then be employed as an input to a second fiber to calculate the transmission losses of a coupler that introduces various coupling inaccuracies, such as lateral offset, axial offset, and angular offset.

A method is used to select a multimode fiber meeting requirements of a first minimum bandwidth at a first wavelength and a second minimum bandwidth at a second wavelength different from the first wavelength. Differential mode delay (DMD) data is measured for the multimode fiber at the first wavelength. The DMD data comprises output laser pulse data as a function of the radial position of an input laser pulse having the first wavelength. The DMD data is transformed into mode group space, to obtain relative mode group delay data as a function of mode group. The multimode fiber is selected based on meeting requirements of the first minimum bandwidth at the first wavelength based on a first set of criteria, comprising a first criterion using as input the measured differential mode delay (DMD) data for the multimode fiber measured at the first wavelength. The multimode fiber is selected based on meeting requirements of the second minimum bandwidth at the second wavelength based on a second set of criteria, comprising: a second criterion using as input the relative mode group delay data. A related system is also described.

An inspecting device has an optical switch selectively coupling a light source unit with each of light input/output ports; a first light detecting unit detecting a first intensity of test light input from an inspecting device on a counterpart side and passing through the optical switch; a second light detecting unit detecting a second intensity of the test light directed from the light source unit toward the optical switch; a third light detecting unit optically coupled to another end of a test optical fiber having one end connected to each of the plurality of light input/output ports, and detecting a third intensity of the test light received from the light source unit via the test optical fiber; and an internal loss recording unit recording a loss of an optical path inside the device obtained on a basis of a difference between the third intensity and the second intensity.

A method of tuning a production module using a reference module with virtual gain correction is provided. The method includes selecting a counterpart reference module created for a select application. The production module is commutatively coupled to the selected counterpart reference module to generate a production module pair. A production module gain curve for the production module pair is measured for each frequency band to be used by the production module. The production module is tuned based at least in part on offset gain values at select number of frequency observation points for each frequency band associated with the counterpart reference module and gain values at the select number of frequency observation points of the measured production module gain curve for each frequency band.

A mode-dependent loss measurement device according to an embodiment of the present disclosure measures a mode-dependent loss of a measurement target optical fiber including a coupled MCF. The device includes a light source, a light receiver, mode coupled state change means, and an analysis unit. The light source inputs light to an input end of an excitation optical fiber including another coupled MCF. The light receiver detects a sum of powers of outputted light beams from a plurality of core end faces positioned on an output end of the measurement target optical fiber. The mode coupled state change means changes a mode coupled state of the excitation optical fiber. The analysis unit obtains a mode-dependent loss of the measurement target optical fiber from variations in optical powers detected by the light receiver.

There is provided a method for measuring the PDL of a DUT as a function of the optical frequency ν within a spectral range, which uses a single wavelength scan over which the input-SOP varies in a continuous manner. The power transmission through the DUT, curve T(ν), is measured during the scan and the PDL is derived from the sideband components of the power transmission curve T(ν) that results from the continuously varying input-SOP. More specifically, the Discrete Fourier Transform (DFT) of the power transmission curve T(ν) is calculated, wherein the DFT shows at least two sidebands. At least two sidebands are extracted and their inverse DFT calculated individually to obtain complex transmissions (ν), =−J . . . J, where J is the number of sidebands on one side. The response vector |m(ν) of the DUT is derived from the complex transmissions (ν) and a matrix determined by the continuous trajectory of the SOP of the input test lightwave; and the PDL of the DUT as a function of ν (PDL curve) is derived therefrom.

A mode-dependent loss measurement device measures a mode-dependent loss of a measurement target optical fiber including a coupled MCF. The device includes a light source, a light receiver, a mode coupled state changer, and an analysis unit. The light source inputs light to an input end of an excitation optical fiber including another coupled MCF. The light receiver detects a sum of powers of outputted light beams from a plurality of core end faces positioned on an output end of the measurement target optical fiber. The mode coupled state changer changes a mode coupled state of the excitation optical fiber. The analysis unit obtains a mode-dependent loss of the measurement target optical fiber from variations in optical powers detected by the light receiver.

A photonic device and a continuous-wave THz signal generator using such photonic device. The photonic device includes an input waveguide arranged to receive input waves of at least two input frequencies and to generate photons at an output frequency associated with the at least two input frequencies; an output waveguide coupled to the input waveguide and arranged to collect the generated photons at the output frequency; wherein the output waveguide is further arranged to facilitate an amplification of the generated photons as the generated photons propagates along the output waveguide and arranged to output an amplified signal at the output frequency.