A test apparatus has at least one optical source, a high-speed photodetector, a microcontroller or processor, and electrical circuitry to power and drive the optical source, high-speed photodetector, and microcontroller or processor. The apparatus measures the frequency response and optical path length of a multimode optical fiber under test, utilizes a reference VCSEL spatial spectral launch condition and modal-chromatic dispersion interaction data to estimate the channels total modal-chromatic bandwidth of the fiber under test, and computes and presents the estimated maximum data rate the fiber under test can support.

An optical receiver can implement a transimpedance amplifier (TIA) to process received light using a closed loop optical pre-amplification. The optical receiver can use an average input value of the TIA to control an semiconductor optical amplifier (SOA) or pre-amplification as received average signal varies. The optical receiver can include a gain controller for the TIA that can measure the TIA swing to adjust the gain of the SOA to pre-amplify received light in a closed loop control configuration.

Low-noise optical differential receivers are described. Such differential receivers may include a differential amplifier having first and second inputs and first and second outputs, and four photodetectors. A first and a second of such photodetectors are coupled to the first input of the differential amplifier, and a third and a fourth of such photodetectors are coupled to the second input of the differential amplifier. The anode of the first photodetector and the cathode of the second photodetector are coupled to the first input of the differential amplifier. The cathode of the third photodetector and the anode of the fourth photodetector are coupled to the second input of the differential amplifier. The optical receiver may involve two stages of signal subtraction, which may significantly increase noise immunity.

Disclosed is an optical receiver. The optical receiver includes a circuit board, a base member, a photodetector mounted on the base member, a transimpedance amplifier, and a capacitor. The base member is disposed between a first grounding pattern and a second grounding pattern on a first side of the circuit board. The transimpedance amplifier is mounted on the first grounding pattern. The capacitor is mounted on the second grounding pattern. The first wiring pattern and the second wiring pattern are apart from both the first grounding pattern and the second grounding pattern in a plan view of the first side. The first grounding pattern is electrically connected to the second grounding pattern through a grounding pattern formed on the first side.

An optical receiver disclosed includes a bias terminal, an input terminal, a photodiode, an amplifier circuit, a first resistor, a bypass circuit, a filter circuit, and a control circuit. The photodiode receives a bias from the filter circuit through the bias terminal, and outputs a current signal to the amplifier circuit through the input terminal. The amplifier circuit converts an input current to an output voltage. The bypass circuit electrically connected to the input terminal decreases a first input impedance viewed from the input terminal, when activated, and increases the first input impedance, when deactivated. The filter circuit increases a second input impedance viewed from the bias terminal, when a dumping function thereof is activated, and decreases the second input impedance, when the dumping function is deactivated. The control circuit activates the dumping function and the bypass circuit, when the output voltage is larger than a certain voltage.

Microstructures of micro and/or nano holes on one or more surfaces enhance photodetector optical sensitivity. Arrangements such as a CMOS Image Sensor (CIS) as an imaging LIDAR using a high speed photodetector array wafer of Si, Ge, a Ge alloy on SI and/or Si on Ge on Si, and a wafer of CMOS Logic Processor (CLP) ib Si fi signal amplification, processing and/or transmission can be stacked for electrical interaction. The wafers can be fabricated separately and then stacked or can be regions of the same monolithic chip. The image can be a time-of-flight image. Bayer arrays can be enhanced with microstructure holes. Pixels can be photodiodes, avalanche photodiodes, single photon avalanche photodiodes and phototransistors on the same array and can be Ge or Si pixels. The array can be of high speed photodetectors with data rates of 56 Gigabits per second, Gbps, or more per photodetector.

An apparatus includes an optical source of an optical wavelength carrier, an optical modulator to receive the optical wavelength carrier, and an optical data receiver. The optical data modulator is configured to produce, from the optical wavelength carrier, an optical signal to carry separate data on different first and second components thereof in individual modulation periods during data transmission and to carry a training sequence on one of the components during time slots for calibration. The first component is relatively phase offset from the second component in the optical signal. The optical data modulator alternates the one of the components between the first and second components over the time slots for calibration. The optical receiver is connected to receive a portion of the optical signal and to temporally interleave a measurement of a characteristic of the first component and a measurement of a characteristic of the second component over the time slots for calibration. The optical receiver is configured to feedback information to the optical data modulator based on the measured characteristics. The optical data modulator is configured to reduce an imbalance between the two components of the optical carrier during data transmission based on the information.

A reception device includes a measurement unit that measures a first number of times for which a first phase and a first reverse phase based on a differential signal obtained by amplifying a signal based on noise intersect with each other, the first reverse phase being a reverse phase of the first phase, an oscillator that transmits a first signal, a comparison unit that compares the first number of times with a predetermined first reference value, and a signal output unit that outputs a second signal indicating that an optical signal has been received when the first number of times and the first reference value coincide with each other. The measurement unit resets the first number of times when the first signal is received.

A photodetecting device includes a substrate, a first photosensitive layer supported by the substrate, and a second photosensitive layer supported by the substrate and adjacent to the first photosensitive layer, each of the first photosensitive layer and the second photosensitive layer being coupled to a first doped portion having a first conductivity type, and a second doped region having a second conductivity type different from the first conductivity type, wherein the first photosensitive layer is separated from the second photosensitive layer, and the first doped portion coupled to the first photosensitive layer is electrically connected to the first doped portion coupled to the second photosensitive layer.

The present disclosure relates to systems and methods for fast digital signal processor (DSP) optical receiver recovery, namely for optical modems configured on a client side. This approach can be used in optical protection switching (OPS) applications to allow switching between two client links fast, i.e., within 50 ms. A receiver (Rx) digital signal processor (DSP) in an optical receiver includes circuitry configured to detect traffic is interrupted on a current link, enter a holdoff period, and one of i) receive good traffic during the holdoff period and ii) have the holdoff period expire that causes a notification to a host device and retrain to acquire an optical signal.