Abstract: An optical receiver (1) comprises a differential TIA (4) linked with a photodiode (2, 3) providing a current sense signal (Isig_tia). The receiver is configured to provide to the TIA a sense signal as a sense TIA input (Isig_tia) and a second input (Idark_tia) which is a proportion of the maximum sense signal. The proportion input is half of said maximum sense signal. The inputs to the TIA are via cascode circuits (5, 6), thereby providing the advantages of a low input impedance for large area photodiodes at the TIA input, while creating a fully differential signal at the output, and the reduction of TIA bandwidth in burst mode applications, which filters out high frequency noise.

Abstract: A supply circuit for providing pulses of current has a current source, a reference voltage source for controlling magnitude of the current, and a current switch for controlling whether or not the current passes through a load. Also, there is a switch control signal terminal for controlling the current switch, and glitch compensation elements including at least one capacitance circuit and associated capacitor drive circuit for feeding a variable correcting voltage back to the reference voltage, and a controller to control said variable voltage.

Abstract: A voltage comparator (1) has a high switching speed and simplicity of design. It minimizes pulse-width distortion of input digital signals when functioning as a digital input buffer in high speed communications applications. In addition it provides a simple hysteresis circuit (31) that is easily tuneable with a reference current. The hysteresis circuit (31) is dependent on a reference current. This current may be chosen to have a proportionality to temperature, supply, or another selectable parameter, and may be programmable, in order to create the desired hysteresis performance.

Abstract: A receiver has a differential transimpedance amplifier (4) with two inputs and two outputs. The differential transimpedance amplifier (4) provides a differential output and this is peak-detected (15, 16) to provide amplitude reference signals. The differential transimpedance amplifier output and the amplitude reference signals are fed to a differential summing amplifier (10), which provides a fully differential signal to a comparator, or to an automatic gain control circuit (5) to regulate the differential transimpedance amplifier gain. The differential summing amplifier (10) output is a fully differential signal, thereby having lower distortion for DC and burst mode receiver applications.

Abstract: A transconductance circuit has an input terminal (VIN) and an output terminal (Out), a first current source (4) having a gate connected to said input terminal (VIN); and a second current source (5), in parallel with said first current source, and having a higher transconductance and a wider dynamic range than the first current source. The current sources are configured so that at a low input voltage only the first current source (4) is on. A voltage drop circuit provides a lower bias voltage for the second current source than for the first current source.

Abstract: A supply circuit for providing pulses of current has a current source, a reference voltage source for controlling magnitude of the current, and a current switch for controlling whether or not the current passes through a load. Also, there is a switch control signal terminal for controlling the current switch, and glitch compensation elements including at least one capacitance circuit and associated capacitor drive circuit for feeding a variable correcting voltage back to the reference voltage, and a controller to control said variable voltage.

Abstract: A voltage comparator (1) has a high switching speed and simplicity of design. It minimizes pulse-width distortion of input digital signals when functioning as a digital input buffer in high speed communications applications. In addition it provides a simple hysteresis circuit (31) that is easily tuneable with a reference current. The hysteresis circuit (31) is dependent on a reference current. This current may be chosen to have a proportionality to temperature, supply, or another selectable parameter, and may be programmable, in order to create the desired hysteresis performance.

Abstract: A receiver has a differential transimpedance amplifier (4) with two inputs and two outputs. The differential transimpedance amplifier (4) provides a differential output and this is peak-detected (15, 16) to provide amplitude reference signals. The differential transimpedance amplifier output and the amplitude reference signals are fed to a differential summing amplifier (10), which provides a fully differential signal to a comparator, or to an automatic gain control circuit (5) to regulate the differential transimpedance amplifier gain. The differential summing amplifier (10) output is a fully differential signal, thereby having lower distortion for DC and burst mode receiver applications.

Abstract: A transconductance circuit has an input terminal (VIN) and an output terminal (Out), a first current source (4) having a gate connected to said input terminal (VIN); and a second current source (5), in parallel with said first current source, and having a higher transconductance and a wider dynamic range than the first current source. The current sources are configured so that at a low input voltage only the first current source (4) is on. A voltage drop circuit provides a lower bias voltage for the second current source than for the first current source.

Abstract: A connector includes a main body, and a pair of sockets. Each socket includes a pair of opposed resilient walls in the overall configuration of a split tube. The connector also includes a transversely sliding clamp with two tapered slots, located so that one of the sockets passes through each slot. After fiber terminations are pushed into the sockets through the clamp slots, the clamp is slid in a plane across the socket axes so that the narrower ends of the slots engage the opposed split tube resilient walls of each socket. This squeezes each socket so that the opposed split tube resilient walls press against the associated fiber termination and retains it in place. The sockets may have guide slots for guiding clamp movement. The clamp moves in a translational movement, but in another example the clamp rotates in the lateral plane to squeeze the sockets.

Abstract: A connector includes a main body, and a pair of sockets. Each socket includes a pair of opposed resilient walls in the overall configuration of a split tube. The connector also includes a transversely sliding clamp with two tapered slots, located so that one of the sockets passes through each slot. After fibre terminations are pushed into the sockets through the clamp slots, the clamp is slid in a plane across the socket axes so that the narrower ends of the slots engage the opposed split tube resilient walls of each socket. This squeezes each socket so that the opposed split tube resilient walls press against the associated fibre termination and retains it in place. The sockets may have guide slots for guiding clamp movement. The clamp moves in a translational movement, but in another example the clamp rotates in the lateral plane to squeeze the sockets.

Abstract: A connector receives and grips an optical fiber in registry with an optical element. Pivoting portions are held in default inoperative position by the spring action of molded hinges, at which position two shutter portions meet, so forming a shutter preventing the ingress of dirt to the optical element. As the optical liber is pushed a small distance into the connector, the pivoting portions are caused to pivot a small amount about the hinges, bringing teeth into contact with the outside jacket of the fiber. The bodies of the inserts are forced radially away from the central axis of the connector, so providing a leaf spring force which keeps the teeth engaged with the jacket of the fiber. The shutter portions move out of the way of the fiber and the spring action applies a force to draw the fiber further into the body of the connector.

Abstract: An optical connector includes four main components, namely a clamp; a housing into which the clamp slides; two optical elements, a transmitter and a receiver; and an EMI metal shield surrounding the elements. The clamp has two parallel through holes for receiving fiber terminations, each through-hole having a generally conical mouth for convenient guidance of a fiber termination. Inside of the through-holes there are side resilient clamp members, and there is a single central clamp member. The clamp is of moulded plastics construction, and the clamp members are resilient in the lateral plane. The central clamp member on the other hand has little flexibility and remains essentially static throughout the clamping operation. Each resilient clamping member has a tooth at its end for snap-fitting engagement with the housing at open and closed positions. Fiber terminations are inserted through the clamp mouths and the through-holes and into the sockets of the housing.

Abstract: An optical connector includes four main components, namely a clamp; a housing into which the clamp slides; two optical elements, a transmitter and a receiver; and an EMI metal shield surrounding the elements. The clamp has two parallel through holes for receiving fiber terminations, each through-hole having a generally conical mouth for convenient guidance of a fiber termination. Inside of the through-holes there are side resilient clamp members, and there is a single central clamp member. The clamp is of moulded plastics construction, and the clamp members are resilient in the lateral plane. The central clamp member on the other hand has little flexibility and remains essentially static throughout the clamping operation. Each resilient clamping member has a tooth at its end for snap-fitting engagement with the housing at open and closed positions. Fiber terminations are inserted through the clamp mouths and the through-holes and into the sockets of the housing.

Abstract: A visible wavelength vertical cavity surface emitting laser suitable for single mode operation has an oxide aperture (81, 82) for concentrating electrical current within a central axial portion (143) of the device and a surface relief feature (144, 146) at an output surface of the device selecting for substantially single lateral mode of operation. The relationship between oxide confinement structure diameter (140) and surface relief feature diameter (141) has been mapped to provide optimum conditions for single mode behaviour and define a region of that space to produce optimum device performance in the visible device operating wavelength band between 630 nm and 690 nm.

Abstract: An optical assembly has a socket for receiving a fiber termination ferrule. A PIN diode is on a lead frame encapsulated in a transparent body. As a fiber ferrule is pushed into the socket the electronic output from the diode is monitored to determine optimum insertion distance.

Abstract: A green LED has a substrate, a GaN heavily n-doped bottom confining layer, an active region, an upper GaN confinement layer, and a semi-transparent ohmic contact layer. The active region has less than or equal to three highly compressively strained quantum wells. The widths of the quantum wells is less than 3 nm. The active region arrangement provides a short free carrier life-time and hence an increase in the modulation bandwidth of the LED.