Abstract: A receiver is described for optical signals which are amplitude modulated with broadband radio frequency signals. The receiver includes an optical detector which receives the incoming optical signal and generates a radio frequency electrical signal which varies with the power level of the incoming optical signal. This electrical signal is applied to a pair of amplifiers which are connected in a push-pull relationship. In a preferred embodiment, a tuning network is connected between the two amplifiers for optimizing the amplification of a selected band of radio frequencies.

Abstract: A light sensor device which uses semiconductors, can assure linearity even with low light intensity, and has a fast response time provides a voltage output proportional to a photoelectric current obtained from the output of an operational amplifier by accumulating the photoelectric current from a photodiode using the operational amplifier and an integration capacitance connected in parallel to the operational amplifier.

Abstract: A circuit arrangement includes a signal source having a high-ohmic complex output impedance, an amplifier having a low-ohmic input impedance for receiving a signal from the signal source, and a tuned quarter wavelength circuit for matching the signal source to the amplifier.

Abstract: An infrared ray receiving circuit includes a band pass filter including two variable transconductance amplifiers, a detector including a differential switch, and a wave-form shaping circuit including a hysteresis comparator. In the infrared ray receiving circuit, the hysteresis width of the hysteresis comparator can be adjusted, so that generation of hair peaks in the output signal of the hysteresis comparator can be avoided. In addition, the generation of an output signal having a pulse width which is shorter than a prescribed pulse width can be avoided.

Abstract: An optical transmitter particularly suited for high frequency applications s disclosed. The optical transmitter successfully operates in harsh environments such as those found in avionic applications. The optical transmitter employs an LED as a light source which cooperates with an active bandpass amplifier to provide a relatively wide bandwidth from about 250 MHz to about at least 1.35 GHz. The bandpass amplifier is selected to have a slope characteristic which is complementary to a roll-off characteristic of the LED and compensates for the high frequency loss of the LED. The slope characteristic of the bandpass amplifier predominates at the high frequencies of the response of the optical transmitter, whereas the frequency response of the LED dominates at the lower frequencies of the response.

Abstract: A switched multi-channel optical receiver having N metal-semiconductor-metal photo-detectors receiving different optical signals, N switches selectively applying a bias voltage to one of the photo-detectors, and a single amplifier. All the elements are integrated in an InP opto-electronic integrated circuit. The switching to a single amplifier allows a reduced number of components.

Abstract: A transimpedance front end is provided for an optical receiver which includes a photodetector coupled optically to an optical fiber for receiving optical signals over the fiber and connected electrically to the front end. The front end comprises a buffer amplifier connected to the photodetector, a first amplifier selectively connected to the buffer through a first switch and through a first, high value feedback resistor in order to define a first mode low optical signal level amplifier configuration, a second amplifier selectively connected to the buffer through a second switch and through a second, switched low value resistor to define a second mode high optical signal level amplifier configuration, and an optical level sensing and switching control circuit connected to the photodetector for sensing incoming optical signal level and for switching between the first and second amplifier configurations as a function thereof.

Abstract: An optical sensing circuit having a photodiode, a differential amplifying circuit, and a comparator. The differential amplifying circuit is provided with an integral capacity. Adjusting capacities are connected in parallel to or disconnected from the integral capacity. A composite capacitance of the integral capacity and the adjusting capacities is adjusted by a control circuit so that the composite capacitance increases with increase of light intensity. This makes it possible to improve sensitivity of the optical sensing circuit for the light intensity and to widen the dynamic range for light sensitivity.

Abstract: An input stage for an optical receiver with a photodiode (T), which has its output connected, via a capacitor (C.sub.1), to the input of a transimpedance amplifier (f), includes a unit having a resistance depending on the voltage, which is connected between the output of the photodiode and the earth potential of the amplifier. The photodiode is a PIN diode, and said unit with a voltage dependent resistance includes a feed-back amplifier (Df) with a frequency response adapted to that of the transimpedance amplifier.

Abstract: A method of detecting the intensity of radiation emanating from an object 116 relative to a background level at a pixel detector 120 is disclosed herein. A resistive element 122 with a resistance dependent upon the intensity of radiation impinging the detector 120 and having first and second terminals is provided along with an integration element 124 coupled to the first terminal of the resistive element. The first terminal is set to a reference voltage. The radiation is then defocused such that the radiation impinging the detector 120 is proportional to the background radiation level and a first voltage is applied to the second terminal of the resistive element 122 such that the integration element 124 discharges to a background voltage level.

Abstract: An edge detector includes a pair of integrated light sensors, a pair of log amplifiers and a comparator amplifier, having a hysteresis voltage applied thereto.

Abstract: A optoelectronic circuit arrangement, for instance for thermal viewing equipment, comprises a plurality of independent photodetector elements, whose signals are combined by multiplexers. The multiplexer output is connected with the common input of a switched integrator, which applies integrated signals to an output switch device, steps being taken to ensure that the multiplexer is at all times electrically separated from the output of the output switch device. For this purpose the integrator has at least one channel with three electronic switching members which in a cyclic sequence perform the operations of "integration", "output of integral value to output" and "erase integral value".

Abstract: A circuit for controlling current flow in an instrumentation loop includes a light sensor receiving impinging light and delivering a signal varying with the intensity of the impinging light. The signal is amplified and produces a reference signal which is a current signal of about four milliamperes in the absence of incoming light and about twenty milliamperes in maximum light. A voltage controlled current driver presents an impedance to current flow through the loop which varies with the reference signal and with the intensity of the incoming light. The sensor includes a mounting plate, a photodetector mounted on the mounting plate, a filter mounted over the photodetector, and a diffuser mounted on the mounting plate forming a dome over the filter and photodetector. The diffuser disperses incoming light before the incoming light impinges the photodetector. The filter blocks infrared light thereby blue enchancing impinging light to approximate the light sensitivity response of a human eye.

Abstract: An integrator having a first circuit including an integrating capacitor and a feedback resistor, both being connected in parallel to each other in a negative feedback loop of the first circuit, and a second circuit, connected to an output side of the first circuit, for compensating for a leak by the feedback resistor. The first circuit operates as an integrator in high frequencies, and as a current-voltage converter in low frequencies. Further, the second circuit compensates for the leak by the feedback resistor, thereby to produce a value indicative of the result of integrating an input current.

Abstract: A front end for a broadband optical receiver is disclosed which includes a monolithic integrated Darlington circuit with bipolar transistors (T1, T2). This Darlington circuit is a simple integrated amplifier (OP) developed for UHF application in the range between 0 and 2 GHz. By connecting a suitable transimpedance resistor (R.sub.T) across the Darlington circuit, an improvement in linearity is obtained such that the Darlington circuit can be used together with an avalanche photodiode (APD) in the 0- to 5-GHz frequency range, and together with PIN diodes in short-and medium-length optical tansmission links.

Abstract: An invention provides a light receiving element which can monitor a light signal input without causing a disturbance in an output signal. A light receiving element has a first active area irradiated by a major component of an input light signal and a second active area irradiated by a leakage light component of the input light signal. An output optical current for information transmission is generated by the light signal radiated on the first active area, and a monitor light output current is generated by the leakage light component of the light signal radiated on the second active area.

Abstract: An amplification device relating to the field of the amplification of ultra-wideband electrical signals from the dc to the microwave range, and more precisely from dc to microwaves of over 6 GHz, notably for the amplification of signals transmitted at very high bit rates on optic fibers, of the type including at least one ampification stage, the active amplification element of which is a field-effect transistor mounted as a common source, each of the amplification stages including means for the simultaneous maintaining of a positive dc voltage bias on the drain of the amplification transistor and a negative or zero dc bias on the gate of the transistor. This device may advantageously be made in monolithic integrated circuit form.

Abstract: An optical receiver includes a photodetecting device and a wide band video amplifier. The photodetecting device and the video amplifier are coupled by reactive elements which are selected to provide a highly linear and highly sensitive response over a frequency range of approximately 400-950 MHz. The crosstalk between two signals are ten parts per billion when the laser power is at 1 milliwatt and modulation is 25 percent per signal. The noise generated by the receiver is only equivalent to 6 billionth of an ampere. The receiver uses commerically available components.

Abstract: A semiconductor optoelectronic device provides full duplex data communication over a single optical fiber. The semiconductor device comprises a unitary P-N light emitting portion and an N-I-P photodiode portion. The light emitting portion and the photodiode portion share a common electrode for connection to operating voltage sources. The second electrode of the light emitting portion contains a window that is associated with one end of the optical fiber. A source of operating voltage for the light emitting portion is connected to the common electrode, and through data controlled switch means and a first resistance means to the second electrode of the light emitting portion. A source of operating voltage for the photodiode portion is connected to the common electrode, and through a second resistance means to a second electrode of the light emitting portion. Differential amplifier means is connected to receive the voltage developed across the first and second resistance means.

Abstract: The present invention aims to provide a fiber optic receiving circuit which can obtain a sufficient frequency band even if a junction capacity of a photo diode is large, wherein a voltage dividing ratio of said voltage dividing circuit, a capacity value of a capacitor, a junction capacity value of a photo diode, and an open loop gain of an amplifier are determined so that current, which flows in the capacitor, cancels current, which flows in a junction capacity of the photo diode and causes frequency deterioration, and the junction capacity of the photo diode, which causes the frequency deterioration, does not relate to an output voltage of the amplifier, thereby obtaining a flat gain characteristic over the broad range of the frequency band regardless of the junction capacity of the photo diode.

Abstract: The invention relates to a circuit array for an optical Schmitt trigger in which an optical input signal is converted into an electrical output signal by means of a light-sensitive receiver element, an amplifier stage, a Schmitt trigger stage and an output stage.It is provided in accordance with the invention that the amplifier stage contains a transimpedance amplifier stage, a differential amplifier stage, a first reference network and a compensating element, that the Schmitt trigger stage comprises a differential amplifier stage, a second reference network and a positive-feedback network, and that the output signal is emitted at the circuit output of the output stage.

Abstract: Optoelectronic positioning tap circuit arrangements of the type in which a beam from a light source irradiates two adjacently arranged diodes connected at their cathode ends and further including an element that is perpendicularly movable with respect to the beam path to partially shade the beam and supply a signal proportional to the difference between the diode currents, such signal characterizing the position of the shading element in the light beam. Sensitivity is increased by utilizing both diode currents to achieve a deflection-proportional output signal by short-circuit current meansurement. Existing current sum points are decoupled as each of the (three) terminals of the series diode circuit is connected to a single current/voltage converter stage. The current sum is directly detected at the input of the voltage converter stage that is connected to the (coupled) cathodes to control the operating point of the light source.

Abstract: Disclosed is an equalizing and amplifying circuit in an optical signal receiving apparatus comprising a preamplifier circuit having an input terminal connected to the output of a light receiving element. The preamplifier circuit amplifies the electrical signal from the light receiving element and outputs an amplified signal. An automatic gain control circuit is connected to the output of the preamplifier circuit. The preamplifier circuit comprises a transistor having a common-base, a current source connected to the emitter of the transistor for supplying a bias current to the transistor, and a load resistor connected to the collector of the transistor. The emitter of the transistor is connected to the input terminal, and the collector of the transistor is connected to the output terminal. A negative influence caused by mounting the circuit on a package is avoided and the circuit operates stably in a high frequency range.

Abstract: An optical receiver incorporating a voltage dependant impedance arranged to shunt excess AC photodetector signal away from the receiver amplifier in response to light level.

Abstract: An electronic receiver circuit for receiving and amplifying optical signals is disclosed. The optical signal is applied to a photodiode which generates a current signal that passes through a source load with a high resistance or impedance relative to the impedances associated with the desired bandwidth of the optical signal. The current signal is amplified and buffered by an amplifier circuit which can drive low output impedances while maintaining the proper voltage level on the high impedance source load. The receiver circuit also maintains a wide signal bandwidth from RF to microwave frequencies, holds pre-amplifier distortion to very low levels and still yields a high signal-to-noise ratio.

Abstract: Where a high bias voltage is required for a photo-element of a photo-receiver, a high voltage is applied to an amplifier which amplifies a photo-current created by the photo-element, when a power supply is turned on. In a prior art photo-receiver, the amplifier may be broken due to this high voltage. In the present invention, the photo-receiver is provided with a protection circuit comprising a diode connected between a power supply circuit and a photo-element, a resistor connected in parallel with the diode, and a first capacitor having one end thereof connected to an anode of the diode and the other end thereof connected to a reference potential. Constants of the circuit components are set such that a time constant of the supply of the power to the amplifier is smaller than a rising time constant of the supply of the power to the photo-element and larger than a falling time constant of the supply of the power to the photo-element.

Abstract: A combined optical power and noise meter for measuring both optical power and optical noise includes a detector housing and a photodiode which is disposed in the detector housing. The resistence of the photodiode changes continually in response to the application of optical power thereon. A current to voltage converter applies a bias voltage to the photodiode and transforms an output current therefrom in order to obtain a power voltage which is proportional to the optical power. A first voltage meter is electrically coupled to the current to voltage converter in order to display the power voltage. A noise measuring circuit measures noise in the output voltage of the current to voltage converter and processes the output voltage in order to obtain a noise voltage which is proportional to the optical noise. A divider divides the noise voltage by the power voltage in order to obtain an optical noise to optical power voltage which is proportional to the ratio of optical noise to optical power.

Abstract: A gain stabilizing amplifier comprises an amplifying transistor for amplifying an input signal; a node for determining a current flowing into the amplifying transistor; a variable current supply connected to the node, a current output from the variable current supply being set to offset variations in a bias current of the amplifying transistor.

Abstract: An optical controlled switch circuit for controlling a two-way voltage drn microwave switch. The optical controlled switch circuit includes, a light source, a control connected to the light source, an optic fiber having an end coupled to the light source, a field effect transistor coupled to a second end of the optic fiber, an inverting dc amplifier means coupled to the field effect transistor, a non-inverting dc amplifier means coupled to the field effect transistor, and a two-way voltage driven microwave switch having signal inputs respectively coupled to the inverting dc amplifier means and to the non-inverting dc amplifier means and having a microwave input and having first and second microwave outputs.

Abstract: A photoelectric switch is adapted for use as either a transmission type or a reflection type switch. To provide an integrated circuit for the photoelectric switch and to minimize input/output pins, multiple functions are assigned to each input/output pin. Such functions are provided via first to fourth integrated circuit input/output pins, i.e., the first pin serves functions in the supply of a detection output and a self diagnosing output; the second pin supports a circuit for driving a projection type LED and a circuit for turning the LED off; the third pin supports a circuit for reversing a stable indication output and an operation indicating output; and the fourth pin supports a circuit for amplifying a received photo-signal and for controlling the mode of combination of photoelectric signals from a pair of photo-diodes.

Abstract: The optical receiver includes a photodiode, a preamplifier and a length of transmission line. The photodiode may be connected to the preamplifier, either via the transmission line, or directly between the preamplifier and the transmission line, that is, the transmission line is connected as an open circuit. The transmission line 14 may comprise a coaxial cable, stripline, or any other suitable form of transmission line. The input impedance of the preamplifier should be designed to match the characteristic impedance of the transmission line. The noise of the preamplifier associated with the transmission line has a periodic spectrum dependent upon the length of the line with peaks at odd multiples of f' and minima at even multiples of f'. The value of f' is related to the length of the transmission line in accordance with: f'=v/4L where v is the propagation velocity, typically 2/3 the speed of light, and L is the length of the transmission line.

Abstract: A circuit arrangement for infrared detectors, more especially for thermal viewing devices with photoresistors as detector elements is designed in order so as not to necessitate an input amplifier and an output amplifier for each detector. For this purpose the collector current of a transistor is integrated for a scan period in a capacitor and at the end of the scan period the capacitor is discharged through an electronic switch to a present potential.

Abstract: A photoelectric switch is adapted for use as either a transmission type or a reflection type switch. To provide an integrated circuit for the photoelectric switch and to minimize input/output pins, multiple functions are assigned to each input/output pin. Such functions are provided via first to fourth integrated circuit input/output pins, i.e., the first pin serves functions in the supply of a detection output and a self-diagnosing output; the second pin supports a circuit for driving a projection type LED and a circuit for turning the LED off; the third pin supports a circuit for reversing a stable indication output and an operation indicating output; and the fourth pin supports a circuit for amplifying a received photo-signal and for controlling the mode of combination of photoelectric signals from a pair of photo-diodes.

Abstract: A transimpedance amplifier comprises a transconductance amplifier having a nonlinear resistive feedback element. The feedback element includes a pair of resistors and a pair of diodes, one of which conducts (depending upon the voltage polarity) only when the voltage across the diode exceeds the diode on-voltage. This includes additional resistance in the feedback element thereby changing the amplifier gain. The largest value of the resistive feedback element is substantially equal to or less than the output resistance of the transconductance amplifier. The feedback element is both symmetrical and nonlinear. A shunt amplifier is driven by circuit which produces a control signal that varies with a signal current. Increasing signal current increases the DC current shunted from the amplifier input thus decreasing pulse edge distortion and increasing dynamic range. A capacitor AC couples the current input to the amplifier.

Abstract: A circuit arrangement for forming the difference and the sum of two detector signals has two photodetectors connected in back-to-back fashion. The difference signal is provided by a first operational amplifier connected to the junction between the two back-to-back connected photodetectors. The sum signal is formed by two further operational amplifiers, whereby one further operational amplifier inverts the signal from one detector and supplies the inverted signal to the input of the other operational amplifier. Thus, the difference signal and the summing signal are directly formed and accessible.

Abstract: In analog communication, a transmission signal must be demodulated with good linearity. However, linearity of a reception signal is often impaired due to a too large input signal or variations during the manufacture of elements or a fluctuation in power supply voltage. According to this invention, a plurality of source-follower circuits constituting a demodulation circuit are formed on a single semiconductor substrate, a resistor having a high resistance is connected between the gate and the source of a first FET, and another resistor is connected to the source. The gate of each of the second and subsequent FETs is connected to the source of the immediately preceding FET, and its source is connected to the gate of the next FET. A product of a gate width of each of the second and subsequent FETs and a resistance of the resistor connected to the source is set to be equal to that of the first FET.

Abstract: A lightwave receiver, suitable for CATV applications, includes an input photodiode that is capacitively coupled to the differential inputs of a balanced amplifier. Biasing of the photodiode may be achieved by connecting the photodiode in series between a pair of resistors, with the differential inputs being taken from either side of the photodiode. This arrangement avoids the use of a transformer, which exhibits considerable high frequency loss, thereby avoiding the bandwidth limitation inherent with a transformer.

Abstract: An optical receiver circuit for an incoming optical signal having a variable power level includes an optical detector for receiving the optical signal and generating a current therefrom which varies with the optical signal power level. The current so generated is applied to a transimpedance amplifier. An automatic gain control (AGC) drive circuit is connected around the amplifier thereby increasing its dynamic range. The AGC drive circuit drives a FET which has one side thereof connected to the transimpedance amplifier for shunting current from the input thereof. A negative feedback circuit comprising an amplifier is connected across the FET, which comprises the resistive feedback element, thus reducing the FET resistance by a factor of 1+T, where T is the feedback circuit loop gain.

Abstract: Current derived from an indium arsenide current generating photodetector is determined accurately, despite the presence of a variable resistance between terminals of the photodetector and the photodetector having leads with appreciable resistance connected to the detector terminals. Two leads are connected to each detector terminal. The two leads connected to one of the detector terminals are respectively connected to an inverting input terminal of an operational amplifier and to one terminal of a feedback resistor of the amplifier; the other terminal of the feedback resistor is connected to the amplifier output terminal. The two leads connected to the other terminal of the photodetector are respectively connected to the operational amplifier non-inverting input terminal and to ground. The operational amplifier derives an output voltage that accurately represents the output current of the photodetector, independently of the photodetector resistance and the lead wire resistance.

Abstract: To extend the dynamic range of an optical receiver with a transimpedance amplifier (TIV), it is known to operate the photodiode (PD) as an AC source at high light levels by using a DC-limiting element in the DC circuit of the photodiode, and to convert, by means of an AC circuit, the alternating voltage into an alternating current serving as the input current for the transimpedance amplifier (TIV), which lies within the permissible range. According to the invention, the AC circuit (C.sub.s, R.sub.s) runs from the photodiode terminal (2) not connected to the transimpedance amplifier input to the output (U.sub.a) of the transimpedance amplifier, whereby an extension of the dynamic range is achieved. The current-limiting element is preferably a transistor circuit (R.sub.E, T) connected as a constant-current source.

Abstract: A logarithmic amplifier comprises an amplifier provided with a feedback circuit, a logarithmic conversion device in the feedback circuit, an oscillation preventing circuit which is provided with a capacitor connected in parallel with the logarithmic conversion device, and a control circuit. The control circuit controls the oscillation preventing circuit in accordance with the current fed into the logarithmic amplifier, so that the amount of certain components in the output from the amplifier, which components are fed back to an input terminal of the amplifier through the oscillation preventing circuit, decreases as the current fed into the logarithmic amplifier becomes smaller. An image read-out apparatus comprises a photoelectric detector which detects light from a recording medium, which light is emitted by the recording medium when it is scanned, and the logarithmic amplifier into which the output current generated by the photoelectric detector is fed. An image having good sharpness is thereby obtained.

Abstract: An optical data medium driving apparatus which constitutes amplifiers for an output current signal of a photosensor including a plurality of current mirror circuits having different amplification factors in order to switch, in a wide range, the output current signal of the photosensor. The photosensor detects a quantity of the reflected light corresponding to a variation of the quantity of reflected light from an optical data medium having various characteristics. The output is obtained with high accuracy and in a wide band. A servo-circuit is used for an AGC circuit and normalizes a difference signal from each light receiving surface at a photosensor having a plurality of light receiving surfaces. An A/D converter is given the difference signal as an analog input signal and the sum signal as the reference input signal. The A/D converter outputs an offset binary type digital signal, thereby being inexpensive to produce, easy to be integrated having high function, and high in reliability.

Abstract: A transimpedance receiver for broad band optical signals, such as carry multichannel CATV signals or broad band data over an optical fiber which may vary in length (e.g. from 2 km to 20 km) such that the optical power at a photodetector of the receiver may vary widely depending upon where the receiver, and is installed in the fiber optic distribution system utilizes a broad band device, preferably a GASFET, the internal capacitance and gain of which enables amplification over the broad band frequency range without oscillation.

Abstract: A receiver circuit for receiving a modulated optical signal and for generating a corresponding electrical signal comprises a photodiode (1) for receiving the optical signal and for generating a first modulated electrical signal. An amplification circuit (3) receives the first electrical signal or a signal related thereto via an n stage (where n is an odd-integer) filter network (2) connected between the photodiode (1) and the amplification circuit (3). The output from the amplification circuit is fed to a first equalization amd noise filter (5). The characteristics of the filter network are such that the total thermal noise power output of the first noise filter is substantially minimized.

Abstract: A current limiter circuit receiving an input current having a non-zero DC component whose value lies in a wide range of current values, and delivering a limited output current whose value lies in a narrower range of current values. The limiter comprises a series connection of a first asymmetrical conductivity element followed by a second asymmetrical conductivity element which is followed in turn by a resistive element, the series connection extending between two poles of a voltage source so that a bias current flows through the asymmetrical conductivity elements and makes them conductive. The input current is applied to the common point between the two asymmetrical conductivity elements and the current-limited output is taken from the common point between the second asymmetrical conductivity element and the resistive element.

Abstract: A system for improving the dynamic range of guidance systems for missiles d bombs by replacing pseudo-logarithmic amplifiers in the processing circuits with transimpedance amplifiers having feed back impedance operating in conjunction with lower bandwidth type logarithmic amplifiers in the log of the ratio circuits.

Abstract: A fiber optic receiver of the type having a sensor, a pre-amplifier and a post-amplifier, includes a first printed circuit board with connection of the post-amplifier therewith and having a matable connector thereon for obtaining power for operation of the post-amplfier. A second printed circuit board is supported by the first printed circuit in intersecting geometric relation to the first printed circuit board and is electrically connected therewith for obtaining power for operation of the pre-amplifier. The pre-amplifier and the sensor are mounted on the second printed circuit board and are electrically interconnected thereon. The receiver further includes a channel for detecting the presence of the carrier of energy incident on the sensor incorporation a differential peak detector circuit. A transmitter may be incorporated to provide a fiber optic transceiver.

Abstract: A preamplifier for a laser rangefinder receiver having two signal level modes comprises, in accordance with this invention, a light detector having a first load resistor, and a buffer having an input connected across the load resistor and an output to the receiver. A first diode is placed in series with a second diode, with the second diode being connected in parallel with a second load resistor. A positive feedback path is provided from the output to the junction of the first and second diodes, wherein the first and second diodes are nonconductive during a low signal level mode, and conductive during a high signal level mode.

Abstract: A circuit arrangement comprises an amplifier that has an input connected to an opto-electrical transducer and a gain which is controllable with the assistance of a control voltage. In order to achieve a great dynamic range given a constant operating point of the amplifier, the drain-source path of a field effect transistor, a feedback path includes a capacitor, and the input of the amplifier is connected to the output of a comparator that compares the output voltage of the amplifier to a reference voltage. The circuit arrangement can be advantageously employed in optical transmission equipment of PCM technology.

Abstract: A multi channel averaging circuit for use with an optical sensing system utilizing back-scattering light for establishing the scattering profile along a fibre sensor, e.g. to determine the temperature distribution along the optical fibre sensor. The circuit comprises a number of connected in parallel, charge coupled devices (3-9) energized by a clock (10) and arranged to store successive elements of a signal waveform derived from the back-scattered light. The stored analogue signals are fed sequentially into the averaging circuit (11), sampled, and then digitized by an A to D converter (13).