Rca Inc.

General Electric Company

Jeffrey P Viola

David R Patterson

Donald Jones Channin

Stefan A Siegel

Joseph B Sergi

Joseph B Sergi, Jr

Roger C Ubben

Thomas Cochran

A fiber optic local area network including a plurality of passive star couplers each capable of connecting to a plurality of users. One connection input to and output from each passive star coupler is connected to a respective output and input of an active star coupler. The active star coupler stores the round-trip transmission times to each passive star coupler and upon receipt of a signal from a passive star coupler inhibits output to that passive star coupler for the signal duration and inhibits input from all other passive star couplers for the signal duration plus the round-trip transmission delay.

Apparatus for connecting multiple passive stars in a fiber optic network

In a burst mode fiber-optic transmitter-receiver or bus interface unit (BIU), the clock recovery process by a phase lock loop (PLL), or more generally a servo loop, detects the frequency difference between the PLL oscillator and the transmitter oscillator, and generates a control voltage which is combined with the voltage controlled oscillator (VCO) error voltage to urge the PLL oscillator towards the transmitter's frequency. An activity detector detects the presence of received signal, and 'freezes' or holds the control voltage to the PLL so the PLL is free to slew to the frequency and phase of the clock of the received burst. Thus, the PLL is maintained near the expected frequency of the received clock signal for fast acquisition. After the burst, the activity detector once again allows the frequency control signal to assert command of the VCO frequency.

Phase lock clock recovery with aided frequency aquisition

A high data rate optical network data communication system includes a receiver including a photodiode detector, a data slicer and a data decision circuit. A clock recovery arrangement includes an impulse generator coupled to the data slicer to generate impulse signals. The impulse generator includes a high speed ECL NOR gate driven by mutually out-of-phase and relatively delayed data. The impulse signals are applied to ring a coaxial cavity by way of a resistor and an input magnetic coupling loop. The coupling loop allows the cavity to achieve high Q so it will oscillate for a relatively long time, and also provides a path by which bias is applied to the output of the NOR gate to fulfill ECL biasing requirements. The cavity Q is maintained high by coupling signals from the cavity by way of a second magnetic coupling loop. The oscillations are applied by way of a limiter to the data decision circuit.

Clock recovery using cavity resonator

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.

Transparent laser drive current update for burst mode fiber optic

In a system for transmitting two level data bursts on a fiber optic (FO) bus, a circuit for turning on a light emitting diode to an excitation level induced by a current I.sub.B corresponding to the knee of the diode characteristic curve and increasing the emitted light in response to a second increasing excitation current over a second portion of the curve beyond the knee extending from excitation level I.sub.B to excitation level I.sub.M. The circuit includes first logic for exciting the diode by the first current, a light responsive device for determining when the emitted light reaches the intensity represented by the knee of the curve and induced by I.sub.B, and logic for reproducibly storing I.sub.B. Second logic responds to the excitation of the diode to the knee of its curve to further excite the diode with the second excitation current until the diode emits a desired light intensity induced by I.sub.B +I.sub.M. Logic is provided for reproducibly storing a signal I.sub.M. Switching logic supplies the current I.sub.M to the diode in response to the data bursts and supplies I.sub. B to the diode substantially concurrently with the data bursts. In the absence of the data bursts the current level I.sub.B is reduced to substantially zero.

Growing community of inventors

Brookhaven, PA, United States of America

Jeffrey P Viola