Abstract: A delay time measurement apparatus for an optical element includes a pulse light source, wavelength setting unit, optical power divider, optical delay unit, controller, and detector. The pulse light source can vary the wavelength of light to be output, and outputs an optical pulse having a predetermined repetition period. The wavelength setting unit sets the wavelength of light to be output from the pulse light source. The optical power divider divides the optical pulse output from the pulse light source into a first optical pulse and a second optical pulse to be input to an optical element as the object to be measured. The optical delay unit can vary the spatial optical path length along which the first optical pulse divided by the optical power divider travels. The controller changes the spatial optical path length of the optical delay unit.

Abstract: A nonlinear optical crystal is composed of 2-adamantyl-5-nitorpyridine (AANP) allowing the type 2 phase matching to the sampling light and a measuring object light, emitting a sum frequency light of the measuring object light and the sampling light, with the polarization directions thereof being perpendicular to each other, when the sampling light and measuring object light multiplexed by a multiplexer are entered. When the sum frequency light is emitted through the nonlinear optical crystal, a control portion controls the polarization direction of the sampling light so as to be parallel to a predetermined reference axis located within a plane perpendicular to a phase matching direction of the nonlinear optical crystal. The predetermined reference axis is a single axis maintaining parallelism with the crystal axis of the nonlinear optical crystal even if the wavelength of the inputted light is changed.

Abstract: A nonlinear optical crystal allowing type 2 phase matching multiplexes a fixed wavelength light having an angular frequency &ohgr;D and a variable wavelength light having an angular frequency &ohgr;S, with the polarization directions thereof being perpendicular to each other, so as to produce a sum frequency light having an angular frequency &ohgr;D+&ohgr;S. When multiplexing the fixed wavelength light and the variable wavelength light through the nonlinear optical crystal, a controlling section controls the polarization direction of the fixed wavelength light so as to be parallel to a predetermined reference axis within a plane vertical to a phase matching direction of the nonlinear optical crystal. Even when the wavelength of inputted light is changed, the predetermined reference axis is a single axis which maintains parallelism with the crystal axis of the nonlinear optical crystal.

Abstract: A common reference signal is applied from the same reference signal generating portion to a reference signal input terminal of a signal under test generator and a reference signal input terminal of a sampling signal generator circuit. A sampling frequency is set to the sampling signal generator circuit such that a desired delay time can be obtained relevant to a phase of a signal under test. In the sampling signal generator circuit, the sampling signal having a cycle that corresponds to the sampling frequency is generated based on the common reference signal and the sampling frequency. A repetition cycle of the signal under test and a repetition cycle of the sampling signal are set based on a cycle of the common reference signal so that the repetition cycle of the sampling signal can be set independently of the repetition cycle of the signal under test.

Abstract: First and second pulse train generating units each generates first and second pulse trains each having a positive polarity and a negative polarity corresponding to one and other polarity elements among positive and negative polarity elements which configure the electric signal in the sine waveform outputted from a signal generating unit. A phase difference setting unit sets the phase difference between the first and second pulse trains so that a pulse of the first and second pulse trains which are generated by the first and second pulse train generating units are partially superimposed temporally. A wave synthesizing unit synthesizes the first and second pulse trains, in which the phase difference. A half-wave rectifying unit half-wave rectifies the output from the wave synthesizing unit and generates a pulse train having a pulse width narrower than any of the pulse widths owned by the first and second pulse trains.

Abstract: A frequency synthesized signal generator outputs a frequency synthesized signal having a frequency equal to a repetition frequency of a signal under test by employing a reference signal. A phase comparator detects a phase difference between a phase of the frequency synthesized signal and a phase of the signal under test, and outputs a phase difference signal. A voltage control oscillator generates a reference signal phase-synchronized with the signal under test based on the phase difference signal output from the phase comparator, and feeds the reference signal back to the frequency synthesized signal generator. A sampling signal generator circuit generates a sampling signal applied to a sampling section by employing the reference signal output from the voltage control oscillator.

Abstract: An optical pulse generator includes a single-wavelength light source, an electroabsorption optical modulator, a sine-wave voltage generator, a nonlinear circuit, and a DC voltage source. The single-wavelength light source outputs continuous, single-wavelength light. The electroabsorption optical modulator receives the single-wavelength light, modulates the single-wavelength light according to a pulse modulation signal, and outputs the modulated light as optical pulses. The sine-wave voltage generator generates an electrical signal having a sine waveform. The nonlinear circuit extracts only a waveform equal to or higher than a predetermined DC voltage from the sine waveform electrical signal. The DC voltage source adds a negative DC voltage to the electrical signal, from which only the waveform equal to or higher than the predetermined DC voltage is extracted by the nonlinear circuit, and applies the sum signal to the electroabsorption optical modulator as the pulse modulation signal.

Abstract: A nonlinear optical crystal is composed of 2-adamantyl-5-nitorpyridine (AANP) allowing the type 2 phase matching to the sampling light and a measuring object light, emitting a sum frequency light of the measuring object light and the sampling light, with the polarization directions thereof being perpendicular to each other, when the sampling light and measuring object light multiplexed by a multiplexer are entered. When the sum frequency light is emitted through the nonlinear optical crystal, a control portion controls the polarization direction of the sampling light so as to be parallel to a predetermined reference axis located within a plane perpendicular to a phase matching direction of the nonlinear optical crystal. The predetermined reference axis is a single axis maintaining parallelism with the crystal axis of the nonlinear optical crystal even if the wavelength of the inputted light is changed.

Abstract: A nonlinear optical crystal allowing type 2 phase matching multiplexes a fixed wavelength light having an angular frequency &ohgr;D and a variable wavelength light having an angular frequency &ohgr;S, with the polarization directions thereof being perpendicular to each other, so as to produce a sum frequency light having an angular frequency &ohgr;D+&ohgr;S. When multiplexing the fixed wavelength light and the variable wavelength light through the nonlinear optical crystal, a controlling section controls the polarization direction of the fixed wavelength light so as to be parallel to a predetermined reference axis within a plane vertical to a phase matching direction of the nonlinear optical crystal. Even when the wavelength of inputted light is changed, the predetermined reference axis is a single axis which maintains parallelism with the crystal axis of the nonlinear optical crystal.

Abstract: A reference signal generation portion generates a reference signal independently of a repetition cycle of a signal under test. A frequency measuring portion measures a repetition frequency of the signal under test by using a reference signal from the reference signal generation portion. A sampling frequency setting portion computes and sets a value of frequency of a sampling signal which can obtain a desired delay time with respect to a phase of the signal under test based on a value of a repetition frequency measured with the frequency measuring portion. The sampling signal generation portion uses a reference signal from the reference signal generation portion and the value of the frequency set by the sampling frequency setting portion to generate a sampling signal having a cycle corresponding to the frequency.

Abstract: A reference signal generation portion generates a reference signal independently of a repetition cycle of a signal under test. A frequency measuring portion measures a repetition frequency of the signal under test by using a reference signal from the reference signal generation portion. A sampling frequency setting portion computes and sets a value of frequency of a sampling signal which can obtain a desired delay time with respect to a phase of the signal under test based on a value of a repetition frequency measured with the frequency measuring portion. The sampling signal generation portion uses a reference signal from the reference signal generation portion and the value of the frequency set by the sampling frequency setting portion to generate a sampling signal having a cycle corresponding to the frequency.

Abstract: A common reference signal is applied from the same reference signal generating portion to a reference signal input terminal of a signal under test generator and a reference signal input terminal of a sampling signal generator circuit. A sampling frequency is set to the sampling signal generator circuit such that a desired delay time can be obtained relevant to a phase of a signal under test. In the sampling signal generator circuit, the sampling signal having a cycle that corresponds to the sampling frequency is generated based on the common reference signal and the sampling frequency. A repetition cycle of the signal under test and a repetition cycle of the sampling signal are set based on a cycle of the common reference signal so that the repetition cycle of the sampling signal can be set independently of the repetition cycle of the signal under test.

Abstract: First and second pulse train generating units each generates first and second pulse trains each having a positive polarity and a negative polarity corresponding to one and other polarity elements among positive and negative polarity elements which configure the electric signal in the sine waveform outputted from a signal generating unit. A phase difference setting unit sets the phase difference between the first and second pulse trains so that a pulse of the first and second pulse trains which are generated by the first and second pulse train generating units are partially superimposed temporally. A wave synthesizing unit synthesizes the first and second pulse trains, in which the phase difference. A half-wave rectifying unit half-wave rectifies the output from the wave synthesizing unit and generates a pulse train having a pulse width narrower than any of the pulse widths owned by the first and second pulse trains.

Abstract: A frequency synthesized signal generator outputs a frequency synthesized signal having a frequency equal to a repetition frequency of a signal under test by employing a reference signal. A phase comparator detects a phase difference between a phase of the frequency synthesized signal and a phase of the signal under test, and outputs a phase difference signal. A voltage control oscillator generates a reference signal phase-synchronized with the signal under test based on the phase difference signal output from the phase comparator, and feeds the reference signal back to the frequency synthesized signal generator. A sampling signal generator circuit generates a sampling signal applied to a sampling section by employing the reference signal output from the voltage control oscillator.

Abstract: A sampling light source generates a pulse sequence of sampling light having a pulse width smaller than that of target light and a single plane of polarization. A polarization beam splitting unit splits each of the sampling light output from the sampling light source, and the target light into two light components having planes of polarization shifted 90.degree. from each other, multiplexes each pair of split sampling and target light components having planes of polarization shifted 90.degree. from each other, and outputs the respective multiplexed light components to different optical paths. A pair of nonlinear optical members each generate a cross-correlation signal based on the sampling and target light components output from the polarization beam splitting unit to each optical path and having planes of polarization shifted 90.degree. from each other as sum frequency light.

Abstract: A first tunable wavelength pulse light source is driven by a reference signal to emit a first optical pulse. An optical demultiplexer demultiplexes a first optical pulse emitted from the first pulse light source into a reference optical pulse and an incident optical pulse to be sent into an object to be measured. An optical multiplexer multiplexes the reference optical pulse and an outgoing optical pulse passing through the object to output multiplexed light. A second pulse light source generates a second optical pulse which is synchronous with the first optical pulse and delays a predetermined time for each period of the first optical pulse. A sampling unit receives the multiplexed light and the second optical pulse to obtain an optical pulse train signal proportional to the intensity of the multiplexed light obtained in synchronism with the second optical pulse.