Other

Ando Electric Company

Nippon Telegraph and Telephone Corporation

Yoshio Endou

Mitsuru Shinagawa

Tadao Nagatsuma

Jun Kikuchi

Nobuaki Takeuchi

Yoshiki Yanagisawa

Junzo Yamada

Nobukazu Banjo

Kazuyoshi Matsuhiro

Nobukazu Banjou

An electro-optic sampling apparatus is provided to enable measurement on potentials of signals on the conductor of coaxial cable with high precision and with ease. Herein, an electric input connector inputs a measured electric signal, which is introduced to a conductive path such as a microstrip line. An electro-optic material (e.g., Bi SiO ) that provides electro-optic effect such as Pockel's effect is fixed to a bare portion of the conductive path and is varied in birefringence ratio in response to strength of electric field caused by the conductive path through which the measured electric signal transmits. The conductive path is then terminated by a terminal device. Now, a laser beam is radiated toward the electro-optic material, wherein it is varied in polarization in response to variations of the birefringence ratio. Then, the laser beam is reflected by a dielectric mirror and is separated into two beams by a polarization beam splitter. Photodiodes are provided to convert the two beams to electric signals representing potentials. Thus, the apparatus measures voltage of the measured electric signal based on the electric signals.

Electro-optic apparatus for measuring signal potentials

An electro-optic sampling oscilloscope (or EOS oscilloscope) uses an electro-optic probe containing an electro-optic crystal, which is placed under effect of an electric field caused by a measured signal. Laser pulses are supplied to the electro-optic crystal wherein they are subjected to polarization. Then, measurement data representative of a waveform of the measured signal are produced in response to polarization states of the laser pulses and are stored in a measurement data storage. A user can select specific measurement data by using a list of files of multiple measurement data which is displayed on a screen. Then, the EOS oscilloscope displays an outline waveform which is created based on a reduced number of sample points extracted from the selected measurement data. Comments and/or measurement conditions can be stored in the measurement data storage in relation to the measurement data, so that they are adequately displayed on the screen.

Electro-optic sampling oscilloscope

In a light receiving circuit for use in electro-optic sampling oscilloscope which receives first and second optical, photodiodes and are connected in series between a positive bias power supply P and a negative bias power supply N. The photodiodes and receive optical signals whose polarization state correspond to the voltage of a signal to be measured and convert the thus-received optical signals into electric signals. An amplifier amplifies an electric current appearing in a point of connection P between the photodiodes and A current monitor detects the electric signal converted by the photodiode and a current monitor detects the electric signal converted by the photodiode The electric signal detected by the current monitor is subjected to analog-to-digital conversion by an analog-to-digital converter and the electric signal detected by the current monitor is subjected to analog-to-digital conversion by an analog-to-digital converter A control section formed from a subtraction circuit controls a ratio of polarization between the optical signals such that the difference between the value of the current detected by the current monitor and the value of the current detected by the current monitor becomes smaller.

Light receiving circuit for use in electro-optic sampling oscilloscope

The present invention relates to an electro-optic sampling oscilloscope. The delay circuit in the electro-optic sampling oscilloscope comprises a delay time detecting circuit, a regulation time determining circuit, a counter circuit and a delay regulating circuit. The delay time detecting circuit detects in the trigger signal a value corresponding to the delay time of a reference clock from a reference clock generating circuit. The regulation time determining circuit determines a regulation time based on the value detected by the delay time detecting circuit so that the regulation time is an integer multiple of the reference clock. The counter circuit is triggered by the trigger signal to count the reference clock through a specific value. The delay regulating circuit employs a signal related to the regulation time from the regulation time determining circuit, to delay the signal output from the counter circuit by the regulation time.

The present invention relates to an electro-optic sampling oscilloscope which carries out measurement of a measured signal using an optical pulse generated based on a timing signal from a timing generation circuit. The timing generation circuit includes a frequency measurement circuit which generates a gate signal for a gate interval which is a specified multiple N of the cycle of the desired sampling rate, and counts the input trigger signals during the gate interval of the gate signal; a division circuit which divides the count value of said frequency measurement circuit by the specified multiple N, and determines a divider ratio; and a frequency divider which divides the trigger signals by the divider ratio determined by the division circuit, and outputs the result as the timing signal.

Timing generation circuit for electro-optic sampling oscilloscope

Timing generation circuit for an electro-optic oscilloscope

The present invention relates to an electro-optic sampling oscilloscope in which an electric field generated by a signal to be measured is coupled with an electro-optic crystal, and an optical pulse outputted from an optical pulse output circuit is caused to enter the electro-optic crystal, and the waveform of the signal to be measured is observed using the polarization state of the optical pulse. The optical pulse output circuit has as the input light thereof a sample optical pulse amplified by an optical amplifier circuit, and outputs, as an optical pulse, the output from an optical filter which blocks the propagation of the spontaneously emitted light of the optical amplifier circuit.

Oscilloscope utilizing probe with electro-optic crystal

An electro-optic sampling oscilloscope (or EOS oscilloscope) is designed to perform measurement such that an electro-optic sampling probe (i.e., EOS probe) is brought into contact with a measured circuit. Optical pulses are input to the EOS probe, wherein they are varied in polarization states in response to the measured circuit. Then, an electric signal output from the EOS probe is amplified to produce a receiving light signal. The receiving light signal is subjected to sampling operations using a first pulse signal to produce detection data, while it is also subjected to sampling operations using a second pulse signal to produce noise data. Herein, the first pulse signal consists of pulses which emerge in synchronization with the optical pulses respectively, while the second pulse signal delays from the first pulse signal by a prescribed delay time. Then, measurement data are produced by subtracting the noise data from the detection data. The measurement data are processed so that a measured waveform representing a measurement result is displayed on a screen of the EOS oscilloscope. Thus, it is possible to obtain the measured waveform with high precision and a good S/N ratio by eliminating low-frequency noise components from the measurement results.

Electro-optical oscilloscope with improved sampling

An electro-optic sampling oscilloscope facilitates adjustment of signal-to-noise ratio caused by electrical, optical and temperature factors. The instrument includes: a light generation section for generation a reference laser beam; a crystal, exhibiting an electro-optic response behavior so as to receive the reference laser beam and to result in changing a refractive index in accordance with electrical field strength generated by target signal; a reflection mirror formed on a rear surface of the crystal for reflecting the reference laser beam that has passed through the crystal; an optical circuit for separating the reference laser beam reflected from the reflection mirror into a first signal light and a second signal light; a first photo-electric conversion section for converting the first signal light into first electrical signals; a second photo-electric conversion section for converting the second signal light into second electrical signals; a differential amplification section for differentially amplifying the first electrical signals and the second electrical signals, and for outputting differentially amplified signals as detection signals of the target signal; and a gain adjustment section for varying gains to adjust a signal-to-noise ratio while the reference laser beam is not being radiated into the crystal, so as to match strength levels of the first electrical signals and the second electrical signals in association with feedback signals of the target signal.

A signal processing circuit is provided for an electro-optic probe, which is used to perform testing of a printed-circuit board of high-speed processing. When laser beams are incident on the electro-optic probe which is brought into contact with the printed-circuit board, they are changed in polarization and are then converted to electric signals. The electric signals are amplified and are then subjected to analog-to-digital conversion to produce digital data. The laser beams (or optical pulses) are generated based on sampling pulses used for sampling of the analog-to-digital conversion. Herein, the sampling pulses are created based on a sweep signal and a step-like signal. The sweep signal increases in level with a certain slope and then decreases suddenly in one period of a trigger pulse signal. The step-like signal increases in level in a step-like manner, wherein it is increased by a predetermined level in response to each of the sampling pulses. A comparator produces a pulse signal consisting of pulses, each of which appears when the sweep signal coincides with the step-like signal in levels. Then, a mask circuit allows output of only the necessary pulses of the comparator as the sampling pulses. An image display circuit stores a plurality of digital data therein, which are then rearranged in an order so that an image representing a measurement result is displayed.

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Tokyo, Japan

Yoshio Endou