Optical star repeater

• US 4,646,361 A
• Filed: 03/08/1984
• Issued: 02/24/1987
• Est. Priority Date: 03/10/1983
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Usui, Takeshi
• Primary Examiner(s): Orsino, Jr., Joseph A.
• Application Number:
  US06/587,643
• Time in Patent Office: 1,083 Days
• Field of Search: 455/601, 455/607, 455/612, 455/617, 370/4, 370/85, 340/825.5
• US Class Current: 398/62
• CPC Class Codes: H04L 12/413 with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]

Abstract

An optical star network for an optical repeater which requires a reduced number of optical receivers.

A star repeater receives optical signals transmitted from various communications terminals and checks for data collisions based on output signals of an optical detector. The star repeater is therefore operable to simultaneously receive numerous optical signals using a single receiver. Upon detection of a data collision, the star repeater generates a jam signal. Each communications station monitors the jam signal to provide communication control. Data collisions are detected based on the fact that the leading and trailing edges of optical pluse signals are detected alternately only when no data collisions occur.

Claims

1. An optical star repeater for use in an optical star network, comprising:

a photoelectric transducer for coupling optical signals from a plurality of receiving paths into a coupled optical signal and for converting said coupled optical signal into an electrical signal;

means for regenerating the electrical signal from the photoelectric transducer to produce a regenerated electrical signal;

means for detecting a collision of the optical signals from said plurality of paths from the electrical signal;

signal generator means for generating a fixed signal;

selecting means, responsive to the detecting means, for selecting said fixed signal in response to a collision indication and for selecting the regenerated electrical signal when no collision is detected;

means for converting the selected signal from the selecting means into an output optical signal; and

means for transmitting the output optical signal into a plurality of transmitting paths;

wherein said photoelectric transducer comprises an optical coupler for coupling together said optical signals from said plurality of receiving paths to provide said coupled optical signal, and an optical receiver for receiving said coupled optical signal,

wherein said optical signals comprise optical code pulse signals and said coupled optical signal comprises coupled optical code pulse signals, and said optical receiver comprises a photodetector connected to the optical coupler to receive the coupled optical code pulse signals and an amplifier connected to said photodetector and operable to generate said electrical signal, and

wherein said electrical signal comprises a series of pulses corresponding to the received coupled optical code pulse signals, said detecting means being operable to detect leading and trailing edges of said pulses for generating a data collision indication responsive to the detection of a plurality of consecutive leading or trailing edges.

2. The optical star repeater of claim 1 wherein said regenerating means comprises a comparator operable to compare said electrical signal to a reference value to regenerate a code pulse from said coupled optical signal.

3. The optical star repeater of claim 1 wherein the fixed signal comprises a repeating pulse pattern.

4. The optical star repeater of claim 1 wherein said detecting means provides a non-collision indication corresponding to a non-collision of optical signals and wherein said optical star network comprises:

means for receiving said output optical signal and for converting same into an electrical pulse signal; and

a gate, responsive to said non-collision indication for passing said electrical pulse signal to an external equipment terminal and responsive to a collision indication for blocking said electrical pulse signal from said external equipment terminal.

5. An optical star repeater for use in an optical star network, comprising:

a photoelectric transducer for coupling optical signals from a plurality of receiving paths into a coupled optical signal and for converting said coupled optical signal into an electrical signal;

means for regenerating the electrical signal from the photoelectric transducer to produce a regenerated electrical signal;

means for detecting a collision of the optical signals from said plurality of paths from the electrical signal;

signal generator means for generating a fixed signal;

selecting means, responsive to the detecting means, for selecting said fixed signal in response to a collision indication and for selecting the regenerated electrical signal when no collision is detected;

means for converting the selected signal from the selecting means into an output optical signal; and

means for transmitting the output optical signal into a plurality of transmitting paths;

wherein said photoelectric transducer comprises an optical coupler for coupling together said optical signals from said plurality of receiving paths to provide said coupled optical signal, and an optical receiver for receiving said coupled optical signal;

wherein said optical signals comprise optical code pulse signals and said coupled optical signal comprises coupled optical code pulse signals, and said optical receiver comprises a photodetector connected to the optical coupler to receive the coupled optical code pulse signals, and an amplifier connected to said photodetector and operable to generate said electrical signal, and

wherein said electrical signal comprises a series of pulses corresponding to the received coupled optical code pulse signals and said detecting means comprises a differentiator responsive to said electrical signal to produce a bipolar signal, a decision circuit operable to receive said bipolar signal and to discriminate between positive and negative pulses thereof, and a logic circuit responsive to an output from said decision circuit to provide a data collision indication whenever a plurality of consecutive positive or negative pulses are detected.

6. The optical star repeater of claim 5 wherein said decision circuit comprises a first and a second comparator, said first comparator being operable to compare said bipolar signal with a first reference voltage greater than an average voltage of said bipolar signal and to produce a positive logic signal when said bipolar signal is greater than said first reference signal, said second comparator being operable to compare said bipolar signal with a second reference voltage lower than said average voltage of the bipolar signal and to produce a negative logic signal when said bipolar signal is less than said second reference signal.

7. The optical star repeater of claim 6 wherein said logic circuit further comprises flip-flop means responsive to an output of said first and second comparators for providing a logic signal having first and second stable states respectively indicative of a data collision and no data collision.

8. A method for transmitting a plurality of received optical code pulse signals in an optical star network having an optical star repeater comprising the steps of:

coupling together said plurality of received optical code pulse signals to provide coupled optical signals;

detecting said coupled optical signals to provide detected optical signals;

converting said detected optical signals into electrical signals comprising a series of pulses corresponding to the received optical code pulse signals;

detecting collisions of said plurality of received optical code pulse signals by differentiating said electrical signals to produce bipolar signals, detecting said bipolar signals, and discriminating between positive and negative portions of said bipolar signals, and producing a collision indication signal whenever a plurality of consecutive positive or negative portions are detected;

generating a fixed signal;

selecting, in response to said collision indication signal, said fixed signal, and, in response to a no collision indication signal, said electrical signal;

converting the selected signal into an output optical signal; and

transmitting the output optical signal to a plurality of optical receivers.

9. The method of claim 8 further comprising the step of regenerating said electrical signal wherein said selecting step includes selecting said regenerated electrical signal in response to a non-collision indication.

10. The method of claim 8 further comprising the steps of:

receiving the output signal;

converting the received signal into an electrical pulse signal;

determining whether said electrical pulse signal is based on said fixed signal or said electrical signal;

passing said electrical pulse signal to an output terminal whenever said electrical pulse signal is based on said electrical signal; and

blocking transmission of said electrical pulse signal to said output terminal whenever said electrical pulse is based on said fixed signal.

11. The method of claim 10 further comprising the steps of:

receiving an input signal from external equipment;

passing said input signal to a memory;

storing said input signal in said memory whenever said electrical pulse signal is based on said fixed signal;

passing said stored input signal from said memory whenever said electrical pulse signal is based on said electrical signal;

converting said input signal into an optical signal; and

transmitting said optical signal to a device for coupling said plurality of optical signals.