Abstract: An apparatus and method for measuring optical signal-to-noise ratio in optical communications includes (1) a variable optical band-pass filter (VOBPF) that passes the amplified output beam when the beam wavelength is the same as the passing wavelength of the VOBPF; (2) a 1×4 beam distributor for distributing the passing beam of the VOBPF into four streams; (3) a measuring device for measuring Stokes parameters S0, S1, S2, S3 from the four distributed beams; (4) a calculating device for calculating the optical signal power by finding the power of the polarized component of the amplified output beam from the Stokes parameters S1, S2, and S3; (5) a calculating device for calculating the noise power by finding the power of the noise included in the amplified output beam from Stokes parameter S0 and the optical signal power; and (6) a dividing device for calculating the ratio Power ⁢   ⁢ of ⁢   ⁢ O

Abstract: The present invention relates to an optical path monitoring device on the basis of the identification of input ports in optical cross-connect systems. An optical path monitoring apparatus in an optical cross-connect system is provided. The optical cross-connect system in accordance with the present invention includes input ports, wavelength-division demultiplexers, optical switching devices, a control device, optical power regulating devices, wavelength-division multiplexers, and output ports. The optical path monitoring apparatus in accordance with the present invention includes a plurality of pilot tone superimposers, a plurality of optical splitters, and a plurality of pilot tone detectors.

Abstract: An optical power divider using a beam separator and a beam expander, and a fabrication method therefor. The optical power divider includes an input optical waveguide having an input port for receiving incident light, for guiding the light incident via the input port, a plurality of output optical waveguides having at least two output ports, for outputting the light incident via the input optical waveguide to the output ports, wherein the number of output optical waveguides is equal to that of the output ports, and a beam separator located at a branch area in which the light incident on the input optical waveguide diverges toward the output optical waveguides, the beam separator being made of a material having a refractive index lower than the core of the input and output optical waveguides, for separating the light to the output optical waveguides with a predetermined ratio. Therefore, the length of the optical power divider becomes short and insertion loss can be lowered.

Abstract: An apparatus for measuring the wavelength, optical power, and an optical signal-to-noise ratio (OSNR) of each optical signal in wavelength-division-multiplexing optical communication includes: elements for splitting a part of wavelength-division-multiplexed (WDM) signals, elements for amplifying the WDM signals and generating spontaneous emission light simultaneously, elements for reflecting a predetermined section of the spontaneous emission light and generating an optical reference signal, and elements for combining the optical reference signal with the part of the WDM signals split by the splitting elements and generating a combined light. The apparatus has components for filtering the combined light at a fixed temperature and generating a waveform which is the same as an optical spectrum of the combined light in the time domain.

Abstract: The present invention relates to a wavelength insensitive passive polarization converter which can rotate the direction of optic axis of waveguide by employing poled electro-optic polymer waveguides and a method for controlling the optic axis direction of the poled polymer waveguides. A passive polarization converter of present invention is equipped with poling electrodes at top and bottom of a planar waveguide consisting of three layers of electro-optic polymer, and it comprises: a polarizer in which poling-induced optic axis aligned horizontally; a polarization rotator in which the azimuth angle of the optic axis is slowly changed along the propagation direction from horizontal to vertical direction; and, an analyzer in which poling-induced optic axis aligned vertically.