JPS60137144A - Photoreceptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a cohesin 1-photoreceiver for detecting an optical signal containing a phase modulated carrier signal with a key phase shift.

It is well known that this type of optical receiver includes a local oscillator whose output signal is mixed with an incoming modulated coherent optical signal to increase the sensitivity of the optical receiver.

In the case of a conventional homodyne receiver, the output from the local excavator has the same frequency as the frequency of the incoming coherent optical signal, whereas in the case of a heterogain receiver, the frequency of the local oscillator is the same as the frequency of the incoming coherent optical signal. IαJ is too large or different from the frequency of the coherent optical signal.

Since a homodyne optical receiver requires that the incoming cohesive optical signal frequency be the same at the local oscillator, the phase of the local excavator needs to be tightly controlled with respect to the incoming cohesive optical signal. This in turn requires a more complex and expensive local oscillator to facilitate phase locking. However, homodyne receivers have -b higher sensitivity than heterodyne receivers (e.g., 3 dB or more sensitivity) due to sideband rejection, and the response speed of the detector is also lower than that of atheroin receivers. It doesn't need to be expensive.

Practical Flow Example According to one aspect of the present invention, an output signal having a frequency that differs by a predetermined m from the frequency of an incoming phase modulated coherent optical signal (hereinafter referred to as the incoming signal) having 111 +1 and ``'0'' signal bits is produced. a local oscillator, a mixer that mixes the output of the local oscillator with the incoming signal, and switches the mixed signal to a respective detector at the fifth signal frequency, thereby increasing the energy output of the mixed signal during the II I I+ bit period of the incoming signal. The receiver includes a switching device effective to send a large proportion of the energy output of the mixed signal to one of the detectors and to send a large proportion of the energy output of the mixed signal to the other detector during the "0" hit period of the incoming signal. ” ;? Served.

In accordance with another aspect of the invention, an output signal having a frequency different from the frequency of the incoming phase modulated cohesin optical signal by a predetermined amount from the frequency of the optical signal having "1" and "O" signal pitches The incoming signal is mixed with the local oscillator output arranged to be phase modulated at an intermediate frequency by a phase modulator before being mixed, and the output is
each detector, thereby directing all or at least a majority of the output of the mixer to one of the detectors during the 171 I+ signal bit periods of the incoming signal and the "0" signal bit period of the incoming signal. A light receiver is provided that includes a light mixer and combiner therein for sending light to other detectors.

In carrying out the last mentioned fourteenth aspect of the invention, the phase modulated signal may be of square waveform or sawtooth waveform, in which case all of the energy output of the mixed signal is the "1" and 1's of the incoming signal. Each detector is manually powered during the II OII Pip 1~ cycle.

For example, three embodiments of the present invention will be described below with reference to the accompanying drawings.

Referring to FIG. 1, the illustrated optical receiver receives an input signal 1 containing a phase-modulated cohesive 1 to optical signal consisting of the order of "phase-shifted 1" and 1101+ signal bits on an optical transmission path.
No. W1 is received. This person's] signal W1 is an output signal W from a local oscillator LX (for example, a Ray IJ" oscillator).
It is mixed with 2. Mixing of the signals W1 and W2 is achieved by a beam combiner or optical coupler (hereinafter mixer) QC.

A second oscillator, P, is synchronized or frequency-locked with the intermediate frequency signal output from the mixer OC, and the output of the oscillator LP is input to an integrated optical device IP, which sends a reading signal W3 to the other. Receive light. This arrangement achieves optical switching of the signal W3 at its frequency, ie at the intermediate frequency, between the two detectors D1 and D2.

Due to the phase modulation due to the key phase shift between the "i" and "0" bits of the input signal, optical switching of the signal W3 causes a relatively high energy output j to one of the detectors (e.g., detector D+). while the other detector (e.g.
Detector D2) generates a low output in response to a '1' beep, and the respective energy outputs for detectors 1 and D2 reverse the above relationship during the period in which a '0' bit occurs. It will be done.

Referring to FIG. 2, phase modulated mixed signal W3 is shown for signal bit 1001. The intermediate frequency output IF produced by oscillator LP is shown just below signal W3, and this signal switches the mixer output between detectors D1 and D2.

Therefore, as can be seen from FIG. 2, during the first "1" bit period, the output from detector D1 is high, whereas the output from detector D2 is low. In response to the occurrence of 11011 bits of signal W3 (key phase shifted), detector D
The output 01)' I G from 1 will be relatively low, whereas the output OD2 from the detector []2 will be high. The resulting average signal output from detector 1]1 and D2 is MD
The overall effect of the arrangement, denoted I and MD2, and therefore described, will be similar to the small modine arrangement mentioned earlier, and will also be a constant with a response speed corresponding to the pill speed of the input signal W1. Allows the use of speed detectors D1 and D2.

Referring to FIG. 3, an alternative embodiment to that shown in FIG. 1 is shown. In this embodiment, a phase modulated optical input signal W1 and a local oscillator W2 are sent from an oscillator Ox to respective input terminals of a four-terminal optical combiner or mixer PX. As shown, the output from mixer PX is sent to detectors D3 and D4, which generate detector outputs OD3 and OD4 (shown above IF), which are at an intermediate frequency. and have opposite phases to each other. However, if the oscillator output signal W2 is phase modulated by a square wave phase modulated signal PS which is synchronized to the intermediate frequency, the detector output (below IF) is OD3
and OD4.

As can be seen, in this example, i+ 1 +
A relatively high output signal OD3 (average output MD3) is outputted from the detector D3 during +bit cycle, and a low output signal 0D4 (average output MD4) is outputted from the detector D4.

In yet another embodiment of the invention, the phase modulation signal for the oscillator output W2 has a sawtooth waveform SW, which causes a phase shift (2π) in the oscillator signal output during each period of the intermediate frequency I F (Wl - W2 > The arrangement achieves a so-called re-login operation.

As can be seen from Fig. 5, this effect is caused by
'' or 110+1, all of one energy is switched to either detector D3 or D4. Therefore, in this embodiment, the detectors are arranged as shown in FIGS. 1 and 3. There is no residual energy in one of the detectors.The average energy output from both detectors is denoted by MSD3 and MSD4.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a light receiver using optical switching, FIG. 2 is a pulse waveform diagram for the light receiver of FIG. 1, and FIG. 3 is a schematic diagram of a light receiver using phase switching.
Figure 4 is a pulse waveform diagram for the optical receiver in Figure 2;
The figure is another pulse waveform diagram for the modification of the light receiver shown in FIG. 3 that performs the serrodyne operation. LX: local oscillator, OC: mixer, LP=oscillator, ■P: integrated optical device (switch), D1 to D4...
・Detector, 1]X: Mixer. Agent Akira Asamura 1 Procedural amendment (method) % formula % 1. Indication of the case 1920 Patent Application No. 19♀No.9bi No. 2, Name of the invention? 9 Evidence 3, Relationship with the case of the person making the amendment Special GV applicant's address (name) 4, Agent 5, Order of amendment Date 1985/Monday 6, number of inventions increased due to amendment 1 issue 9 of drawings (No change to B 6)

Claims (1)

[Scope of Claims] (1) An incoming phase-modulated coherent optical signal that modulates the "1" and "0" signal bits, that is, a local part that generates an output signal having a frequency that differs by a predetermined amount from the frequency of the incoming signal. an oscillator and a mixing device for mixing the local oscillator output with the incoming signal; at least a major portion of the output from the mixing device is sent to one of the detectors during a "1" signal bit period of the incoming signal; “O” signal beep 1-
a device coupled to the mixing device effective for generating an output to the side detectors at a mixing signal frequency to be sent to other detectors during a cycle; Features and Juru receiver. (2) A local oscillator that generates an output signal having a frequency that differs by a predetermined amount c from the frequency of the incoming phase-modulated coherent optical signal that right-centers the "1" and "OI+ signal pits, that is, the frequency of the incoming signal, and the local oscillator output. a mixing device for mixing the incoming signal with the incoming signal, and a large proportion of the energy output of the incoming signal during the incoming signal's '1' bit period is sent to one of the detectors and the 'O' bit period of the mixed signal is −
A large proportion of the energy output during a cycle is sent to the other detectors, characterized in that it includes a switching device effective to switch the mixed signal to the four detectors at the frequency of the mixed signal. light receiver. (3) a local oscillator that generates an incoming phase modulated coherent optical signal having "1" and "O" signals, that is, an output signal having a frequency that differs by a predetermined maximum amount from the frequency of the incoming signal; The incoming signal is mixed with a local oscillator output which is arranged to be phase modulated at an intermediate frequency by a phase modulator before being mixed and all or at least a majority of the output signal from the mixing device is tti
The recorded unarrived signal 1'' signal is sent to one of the detectors during the 1-period and the incoming signal's ``O''(; (4) In the light receiver according to claim 2, the mixing device is a beam combiner. or an optical coupler. (5) In the light receiver according to claim 2 or 4, the switching device is synchronized with the intermediate frequency of the output of the mixing device. or an integrated optical device arranged to be switched by the output of a frequency-locked oscillator. (6) The optical receiver according to claim 3,
The optical receiver is characterized in that the phase modulator supplies a square wave phase modulation signal. (7) In the light receiver according to claim 3,
A signal that undergoes phase modulation (a sawtooth waveform in which all of the energy output of the mixed signal is R of the incoming signal)
Said photoreceiver, characterized in that it is input to each detector during an I11 or '0'' bit period.