Abstract: A burst mode fiber optic or light-wave communication system uses as a transmitter a light emitting device requiring drive current to produce a light output. The characteristics of the light emitting device change with time, so the drive current must be periodically adjusted. In a high speed burst data system, the magnitude of the light output and the new value of drive current cannot be determined until a time well after the beginning of the burst, or possibly after the burst has ended. If the drive current is adjusted to a new value during burst transmission, the change in light output may be interpreted by a receiver as a data transition, which may result in data errors. The change in the control signal which controls the magnitude of the drive signal is delayed until a time between data bursts, whereby the drive current magnitude remains constant during any burst transmission.

Abstract: A fiber-optic communication system for data bursts includes a plurality of nodes, each including a laser diode transmitter. In order to reduce the noise floor of the system, each laser diode receives bias current only when it is transmitting data. Due to the propagation delay between nodes, there is a dead time between data bursts received by each node during which no data signals are received. The bias current of the laser diode is adjusted following each data transmission, so that the light attributable to laser operation during the setting of bias is received during the dead time. The adjustment is accomplished by stepping an up-down counter by one clock pulse following transmission of each data burst.

Abstract: An optical fiber-ring network is disclosed. The network is capable of operating in the face of the failure of any single node regardless of the particular node failure mechanism, including stuck "on" and stuck "off" transmitters.Each node in the network comprises a main receiver, an alternate receiver, and a transmitter. The main receiver receives data from the immediately adjacent upstream node, while the alternate receiver monitors transmissions from the next preceding upstream node. Each node diagnoses the transmitter in its immediately adjacent upstream neighbor and its own main receiver. If either fails, the node switches from its main receiver to its alternate receiver to bypass the immediately adjacent upstream node, while the rest of the ring remains functional.

Abstract: The propagation speed of optical solitons in single mode optical fiber depends on the wavelength of the solitons. Thus, if solitons of different wavelengths are co-propagating, "collisions" between pulses can be expected to result. It has been found that collisions between solitons do preserve the soliton character of the colliding pulses, even in the presence of perturbations of the type present in fiber communications systems, e.g., core size variations, distributed or lumped loss, and distributed gain. Thus, a wavelength division multiplexed soliton system is possible, and techniques and formulae for the design of such systems are disclosed. In preferred embodiments, fiber loss is periodically compensated by Raman gain. Typical amplification periods (using currently available silica-based fiber) are 30-50 km, typical pump powers are less than 100 mV, and rate-length products of the order of 3.multidot.10.sup.5 GHz km are possible.

Abstract: A simultaneous bi-directional transceiver is described. The transceiver comprises two circuits which are disposed at opposite ends of an interchip cable. In response to the application of digital data signals to these circuits, they generate a trilevel voltage at the ends of the interchip cable. Then, in each circuit, a first input to a differential amplifier is generated from the trilevel voltage by a level shifter comprising a first diode and a first constant current sink and a second input to the differential amplifier is derived from the digital data input signal applied to that circuit by a level shifter comprising a second diode and a second constant current source. Finally, the transceiver outputs are generated from the differential amplifier outputs.

Abstract: A T-connection fiber-optical repeater employs redundant electrical-to-optical converters for generating optical signals to be distributed to terminal devices connected the repeater, and redundant optical-to-electrical converters for receiving optical signals from the terminal devices. Reliability is markedly increased by including one or two mixing stars in the fiber system between the converter and the repeaters. The number of converters and supporting circuitry that is needed can be reduced by coupling more than one fiber from the star or stars to each converter. The reliability of the repeater can be further enhanced by using redundant optical-to-electrical converters to receive optical signals from other repeaters and by using redundant electrical-to-optical converters to emit optical signals to other repeaters. Monitoring optical-to-electrical converters can be coupled to the stars in order to detect failure of electrical-to-optical converters connected to the stars.

Abstract: The novel technique for stabilizing an electronic device, e.g., a semiconductor laser, is disclosed. The technique can advantageously be used to stabilize the bias current of such a laser at or near the lasing threshold of the device. A preferred application of thus stabilized lasers is in optical communication systems. The inventive technique comprises determination of a derivative of a variable characteristic of the device operation, e.g., the voltage across a laser, with respect to a parameter, e.g., the laser bias current. The derivative is determined by a novel method. For the particular case of laser bias stabilization, the method comprises injecting one or more nonsinusoidal ac current components into the laser, and phase-sensitivity detecting the voltage changes at the ac frequencies. The method can, in principle, be used to determine derivatives of arbitrarily high order.