Abstract: An optical pulse tester includes an optical divider configured to cause a return light to divide into first divided light and second divided light, a first optical receiver configured to receive the first divided light and output a first optical receiver signal, a second optical receiver configured to receive the second divided light and output a second optical receiver signal, and a signal processor configured to obtain a waveform indicating an intensity distribution of the return light in a longitudinal direction of the optical fiber by performing level conversion of the first optical receiver signal and the second optical receiver signal on the basis of a divided ratio of the optical divider and optical receiver sensitivities of the first optical receiver and the second optical receiver and synthesizing the first optical receiver signal and the second optical receiver signal which have been subjected to the level conversion.

Abstract: An optical pulse tester is for testing characteristics of an optical fiber on the basis of return light obtained by causing an optical pulse to be incident on the optical fiber. The optical pulse tester includes a plurality of light source elements configured to emit optical pulses of different wavelength bands, a plurality of light receiving elements provided to correspond to the plurality of light source elements, a first spatial optical system in which the optical pulses emitted from the plurality of light source elements are spatially combined by wavelength to be incident on the optical fiber, and a second spatial optical system in which return light from the optical fiber is spatially separated by wavelength to be incident on the plurality of light receiving elements.

Abstract: The invention is to provide an optical loss measuring method and an optical loss measuring apparatus capable of efficiently measuring an optical loss occurring to a target for measurement. The other optical loss measurement method comprising the steps of inputting light outputted from a light source to a target for measurement to thereby measure an output level of the target for measurement with the use of an optical power meter, maintaining the output level of the light source at a predetermined fixed value, and finding the optical loss occurring to the target for measurement on the basis of the output level of the light source maintained at the fixed value for use as the reference value.

Abstract: The invention is to provide an optical loss measuring method and an optical loss measuring apparatus capable of efficiently measuring an optical loss occurring to a target for measurement. The other optical loss measurement method comprising the steps of inputting light outputted from a light source to a target for measurement to thereby measure an output level of the target for measurement with the use of an optical power meter, maintaining the output level of the light source at a predetermined fixed value, and finding the optical loss occurring to the target for measurement on the basis of the output level of the light source maintained at the fixed value for use as the reference value.

Abstract: Optical fiber characteristic measuring device comprising a coherent light supply device, a light pulse generating device, a wave mixing device, a opto-electrical converting device, and a processing device, is provided such that parts have the frequency characteristic for corresponding to low frequency component for an opto-electrical converting device and a processing section so as to reduce the cost of the circuits.

Abstract: optical fiber characteristic measuring device comprising a coherent light supply device, a light pulse generating device, a wave mixing device, a opto-electrical converting device, and a processing device, is provided such that parts have the frequency characteristic for corresponding to low frequency component for an opto-electrical converting device and a processing section so as to reduce the cost of the circuits.

Abstract: The present invention provides an optical fiber distortion measuring apparatus and optical fiber distortion measuring method which make it possible to measure the amount of distortion of an optical fiber efficiently and in a short period of time. The time change waveform when a light pulse having a frequency of &ngr;1 is applied is compared with initial data (the time change waveform obtained in a case in which there is no distortion). Then, the light intensity L1 at a position Dx at which the light intensities do not agree is obtained. Next, the time change waveform is measured when a light pulse having a frequency of &ngr;2 is applied, and the light intensity L2 at position Dx is obtained. After this, the loss (resulting from distortion) in light intensities L1 and L2 is corrected, and light intensities LC1 and LC2 are obtained.

Abstract: The present invention relates to an optical-fiber characteristics measuring apparatus that does not require frequency conversion of pulse light which enters an optical fiber to be measured, and does not restrict the cycle period of the pulse light, thereby ensuring fast measuring of the characteristics of the optical fiber. This apparatus comprises an optical directional coupler, an optical pulse generator, a balanced-light reception circuit, a signal generation section and a mixer. The optical directional coupler branches coherent light into first and second coherent lights. The optical pulse generator converts the first coherent light into pulse light which in turn enters an optical fiber to be measured. Returned light whose frequency is shifted from that of the first coherent light by a predetermined frequency through reflection and scattering in the optical fiber to be measured enters the balanced-light reception circuit.

Abstract: The output light from a light source 10 is incident upon an optical fiber to be measured via an optical directional coupler 11, an optical switch 12, an optical amplifier 13, and an optical directional coupler 14. Light from the optical directional coupler 11 is incident upon a polarization controller 16. The output light from the polarization controller 16 and light returned from the optical fiber 15 are incident into an optical balance circuit 17, and these light are interfered. A fixed frequency, or alternatively a frequency which is varied stepwise, is output from a voltage control oscillator 18, according to a control signal from a DC voltage generation circuit 19 or from a saw tooth wave generation circuit 20. The output of the optical balance circuit 17 and the output of the voltage control oscillator 18 are mixed together by a mixer 26.

Abstract: There is provided an apparatus for measuring the characteristics of an optical fiber in which a frequency difference between first and second coherent light respectively generated by first and second light sources can be accurately set and wherein preferable coherent detection can be carried out in accordance with frequency components of returned light. First coherent light at a frequency f1 is converted into a pulse light which is output to the optical fiber to be measured. The characteristics of the optical fiber are measured by multiplexing returned light from the optical fiber to be measured and second coherent light at a frequency f2 and by detecting the multiplexed light. A component .vertline.f1-f2.vertline. is detected from an optical signal obtained by the multiplexed light and is mixed with a signal at a frequency fr to decrease the frequency. An electric signal at a voltage level corresponding to a differential frequency .vertline.f1-f2.vertline.

Abstract: An optical fiber distortion measurement system (i.e., device and method) measures an optical fiber, which is constructed by alternately connecting two kinds of optical fibers whose Brillouin frequency shifts are different from each other. The system sequentially supplies optical pulses to the measured optical fiber while changing their light frequencies, so that Brillouin backscattering beams are output from the measured optical fiber. At first, the system supplies an optical pulse having a prescribed light frequency to the measured optical fiber of a non-distortion state, so that the device produces initial data representing time-related variations of light intensity of Brillouin backscattering light output from the measured optical fiber. Then, the system measures a time-related variation waveform representing light intensity of Brillouin backscattering light, which is output from the measured optical fiber supplied with the optical pulse of the prescribed light frequency.

Abstract: The objective of the present invention is to offer an optical fiber strain-measuring apparatus, which allows the detecting of the amount of strain at an arbitrary distance within a test optical fiber as well as the distance strain distribution, and facilitates the detecting of the back scattered light.

Abstract: An object of the present invention is to provide an optical fiber strain measuring apparatus which can perform precise measurement without causing any fluctuation in signal level.

Abstract: The objective of the present invention is to offer an optical fiber strain-measuring apparatus, which allows the measurement of the strain at an arbitrary position within an optical fiber. An optical frequency conversion section 3 shifts, in a step-wise manner for prescribed frequencies, the frequencies of a continuous light emitted from a light source 1. A sound-light switch 4 coverts into pulses the continuous light forwarded from the optical frequency conversion section 3. When those light pulses are entered into a test optical fiber, back-scattered light is generated. An optical directional coupler 11 branches and forwards to an optical ring circuit and to an optical directional coupler 13 the back-scattered light. A photo-electric converter 14 receives employing heterodyne detection and converts into electric signals the synthesized light signals of the back-scattered light forwarded from the optical directional coupler 11 and the continuous light forwarded from the optical directional coupler 2.

Abstract: An optical pulse signal produced by modulating a continuous laser light by means of a first pulse having a period sufficiently shorter than the atomic lifetime in the upper energy state of a rare earth doped fiber is input to an optical amplifier to be measured, while an output signal from the optical amplifier is modulated by a second pulse synchronized with the first pulse and having a phase difference relative to the first pulse which can be optionally set so that rapid phase adjustment relative to the first pulse is possible based on the phase at the time of minimum optical power. The noise figure of the optical amplifier is then measured based on, the maximum photoelectric power (P.sub.AMP +P.sub.ASE) and the minimum photoelectric power P.sub.ASE of the resultant optical signal.

Abstract: An OTDR measurement device employs optical heterodyne wave detection to perform measurement on optical fibers. Optical pulses are incident on a measuring optical fiber, which in turn outputs backward scattering light. The device performs heterodyne wave detection on the backward scattering light as well as probe light whose frequency is set in proximity to a frequency of the backward scattering light, thus producing a detection voltage. The device provides a differential amplifier which performs amplification on a difference between the detection voltage and a reference voltage to produce a difference signal. An A/D converter converts the difference signal to a digital signal. Square addition is performed on the digital signal to produce a mean square signal representing property of the measuring optical fiber. Herein, calculations are performed on the mean square signal to produce a reference signal, which is then converted to the reference voltage.

Abstract: The present invention provides light frequency control apparatus comprising a light pulse signal generating mechanism for generating a light pulse signal of a standard frequency; a light frequency shifting mechanism for circulating this light pulse signal a predetermined number of times, delaying this light pulse signal at each cycle thereby sequentially shifting and outputting the aforementioned light pulse signal; an extracting mechanism for extracting a light pulse signal in the second half of a cycle from the output of the light frequency shifting mechanism; and a polarization control mechanism inserted into the light frequency shifting mechanism for controlling the angle of polarization of the light pulse signal circulating in the light frequency shifting mechanism based on the amount of attenuation of the light pulse signal outputted by the extracting mechanism.

Abstract: A simple, quick and precise method for determining a noise factor of an optical amplifier system is presented and demonstrated with an apparatus based on rare-earth doped optical fibers. The method is based on rapid adjustments of the phase differentials between the input optical signals into and the output optical signals from the optical amplifier to compensate for system variables including the optical fiber lengths within the apparatus as well as in the ancillary devices. A cw laser source is modulated with a first pulse having a significantly shorter cycle than a lifetime of excited atoms within the doped fiber, and the modulated pulses are continually applied to the noise determining apparatus. The optical output signal from the apparatus is synchronized with the first pulse and the optical output signal is further modulated with a series of second pulses having increasing phase differentials in relation to the first pulse.

Abstract: The present invention provides light frequency control apparatus comprising a light pulse signal generating mechanism for converting continuous light into a light pulse signal, and outputting this light pulse signal; a light signal generating mechanism for repeatedly generating at predetermined cycles, a light signal, in which a light frequency component therein is shifted to form a staircase shape based on the number of cycles of a loop within which the light pulse signal circulates; and a dummy light generating mechanism for generating dummy light at a timing such that the level of the light signal becomes zero, and supplying this dummy light to the light amplifying mechanism. The aforementioned loop is formed from a light amplifying mechanism for amplifying the light pulse signal outputted from the light pulse signal generating mechanism, light delay mechanism for delaying the light pulse signal a fixed amount; and frequency shifting mechanism for shifting the frequency of the light pulse signal.

Abstract: A reference light generating mechanism generates reference light, a light frequency component of which varies in a stepped manner at fixed intervals, repeatedly at pre-specified cycles, and generates a timing signal in accordance with this variance. A detecting mechanism detects a frequency difference between a reference light frequency freely selected from among the light frequency component and a feedback light frequency of feedback light fed back so as to conform to the reference light frequency, and synchronizes this with a timing signal, and an output light generating mechanism generates output light, the light frequency of which is controlled in accordance with the frequency difference, and conducts the feedback of this output light to the detecting mechanism as feedback light.