KR20160050925A - Method and Apparatus for Synchronizing using Opto-electronic Oscillator - Google Patents

Abstract

A method and an apparatus for synchronizing transmission and reception using a photoelectric oscillator are disclosed.
According to an aspect of the present invention, there is provided a transmission / reception synchronization method and apparatus in which a transmitter and a receiver share an oscillation frequency that varies depending on disturbance or the like applied to an optical fiber by using an optical fiber between a transmitter and a receiver as a resonator of a photoelectric oscillator do.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and apparatus for synchronizing transmission and reception using a photoelectric oscillator,

The present embodiment relates to a transmission / reception synchronization method and apparatus using a photoelectric oscillator. More particularly, the present invention relates to a transmission / reception synchronization method and apparatus in which a transmitter and a receiver share an oscillation frequency that varies depending on disturbance or the like applied to an optical fiber by using an optical fiber between a transmitter and a receiver as a resonator of a photoelectric oscillator.

The contents described in this section merely provide background information on the present embodiment and do not constitute the prior art.

A typical synchronous data communication system includes a transmitter, a communication channel, and a receiver. In such a system, the receiver must be able to reliably decode information sent by the transmitter over the channel. To do this, the receiver samples the input signal at an appropriate point in time and makes various decisions. The clock that the transmitter uses to transmit the data signal is generally referred to as a "reference" clock. Typically, timing information is extracted from the phase of the input signal using a clock recovery circuit such as a phase lock loop (PLL) in the receiver. This clock is commonly referred to as a "recovered" clock. To minimize bit errors, the playback clock should be closely matched to the reference clock.

However, noise in the channel and defects in the receiver cause a phase change in the input data signal. Particularly, in the long-distance transmission, a phase difference of a synchronous signal occurs due to temperature change of the optical fiber or mechanical vibration. This causes a change in the phase of the reproduced clock relative to the reference clock, thereby increasing the error occurrence probability. A phase change or phase variation at a significant point in time of a data signal is called jitter. Jitter control is important because jitter degrades the performance of the transmission system and causes bit error and uncontrolled slip in the digital signal. Jitter causes a bit error by interfering with accurate sampling of the digital signal by the clock recovery circuit. Effective management of jitter is important for creating systems with acceptable bit error rates.

In order to control the jitter, a technique of controlling jitter by a method of detecting a noise of a fiber at a transmitting end and compensating the noise at a transmitting end by transmitting a part of a signal transmitted through an optical fiber is returned from a receiving end. A jitter control system of this type is schematically shown in Fig.

The present embodiment provides a transmission / reception synchronization method and apparatus in which a transmitter and a receiver share an oscillation frequency that varies depending on disturbance or the like applied to an optical fiber by using an optical fiber between a transmitter and a receiver as a resonator of a photoelectric oscillator .

According to an aspect of the present embodiment, there is provided a transmission apparatus of a synchronous data communication system, comprising: a laser which forms an optical oscillation in response to an electrical modulation control signal; 1. An opto-electronic feedback loop having a loop gain greater than one, the opto-electronic loop having a loop gain greater than one, An electro-optical loop for converting a signal into the modulation control signal related to the optical oscillation; And a transmitter optically connected to the electro-optical loop to obtain a part of the optical signal output by the laser and use the obtained optical signal as a carrier wave.

Wherein the opto-electronic oscillator includes: a light splitter for dividing an optical signal output from the laser into a first optical signal and a second optical signal; A optical rotator optically connected to the optical splitter to transmit the first optical signal to the transmission line fiber and receive a reflection signal of the first optical signal received from the transmission line fiber; A photodetector for detecting a reflected signal of the first optical signal; And an electronic circuit for generating the modulation control signal from an output of the photodetector.

The electronic circuit comprising: a band-pass filter for selecting a desired oscillation frequency of the laser; And an amplifier for amplifying an output of the band pass filter to generate the modulation control signal.

로 표현될 수 있다. 여기서, 상기

는 발진 주파수, 상기

은 모드 수로서 임의의 정수, 상기

는 매질 속 전자기파의 속도이다.The oscillation frequency of the laser is

. ≪ / RTI > Here,

The oscillation frequency,

Is an arbitrary integer as the number of modes,

Is the velocity of the electromagnetic wave in the medium.

The transmission apparatus further includes a second optical-optical loop 310 in which a short optical path 310 not passing through the transmission path fiber 400 is optically connected in parallel with the electro-optical loop (hereinafter referred to as a first electro-optical loop) . Here, it is preferable that the optical path of the second electro-optical loop does not pass through the transmission path fiber.

According to another aspect of the present invention, there is provided a synchronization method of a transmitting apparatus and a receiving apparatus in a synchronous data communication system, the method comprising: transmitting a transmission path fiber between the transmitting apparatus and the receiving apparatus as a part of an optical path, The transmission apparatus uses a part of an optical signal output from the laser as a carrier wave and the receiving apparatus forms a part of an optical signal transmitted through a transmission path fiber And a synchronization method for a receiving apparatus of the synchronous data communication system.

As described above, according to the present embodiment, since the optical-electronic feedback loop includes the transmission line fiber as the optical path, the optical delay of the transmission line fiber (Optical Delay) changes, the transmitter and the receiver sharing the oscillation frequency on the opto-electronic feedback loop share the same oscillation frequency, even though the oscillation frequency of the opto-electronic feedback loop changes.

Fig. 1 schematically shows a conventional jitter control system.
FIG. 2 is a diagram schematically showing a configuration of a transmission / reception system for synchronizing using a photoelectric oscillator according to an embodiment of the present invention. Referring to FIG.
FIG. 3 is a diagram schematically showing a configuration of a transmission / reception system for synchronizing using a photoelectric oscillator according to another embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. Throughout the specification, when an element is referred to as being "comprising" or "comprising", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise . In addition, '... Quot ;, " module ", and " module " refer to a unit that processes at least one function or operation, and may be implemented by hardware or software or a combination of hardware and software.

FIG. 2 is a diagram schematically showing a configuration of a transmission / reception system for synchronizing using a photoelectric oscillator according to an embodiment of the present invention. Referring to FIG. 2, the transmitting unit 100 and the receiving unit 130 may include an opto-electronic oscillator (hereinafter, referred to as " Opto-electronic Oscillator " ).

The optoelectronic oscillator includes a laser for generating pulsed light based on the modulation control signal. The laser may include a diode (Laser Diode) 210, as illustrated in Figure 2, in some embodiments, a multimode solid state laser, a diode pump laser,

In some other embodiments, the optoelectronic oscillator may comprise a laser diode (LD) for generating pump light and an optical modulator for modulating the output of the laser diode based on the modulation control signal to produce modulated light .

The pulse light generated in the laser diode 210 meets the optical splitter, a part of the pulsed light is transmitted to the transmission unit 100, and the rest is transmitted to the optical circulator 230. In FIG. 2, it is assumed that the 10% reflector 220 transmits 10% of the pulsed light to the transmitter 100 and the remaining 90% to the optical rotator 230.

The optical rotator 230 has three ports (Port 1, Port 2, and Port 3), transfers light received at port 1 to port 2, and transmits light received at port 2 to port 3. Port 1 is optically coupled to the 10% reflector 220 via fiber or free space to receive input light from the 10% reflector 220. The port 2 is optically connected to the transmission path fiber 400 through a fiber or free space to transmit the input light transmitted from the port 1 to the transmission path fiber 400 and to transmit the reflected light received from the transmission path fiber 400 To port 2. The port 3 is optically connected to the photodetector 250 via fiber or free space to transmit the reflected light transmitted from the port 2 to the photodetector 250.

The input light transmitted from the port 1 of the optical rotator 230 to the transmission line fiber 400 meets a light splitter located in the transmission line fiber 400 on the reception side. 2, it is assumed that the 90% reflector 240 reflects 90% of the input light and transmits the remaining 10% to the receiver 300.

The optoelectronic oscillator also includes a photodetector 250 for detecting the reflected light transmitted from the optical rotator and an electronic circuit for generating a modulation control signal from the output of the photodetector 250. 2, the electronic circuit amplifies the output of the RF filter 260 and an RF filter (e.g., a bandpass filter) 260 for selecting a desired oscillation frequency and outputs the modulated control signal of the laser diode 210 And an RF amplifier 270 for generating an RF signal. The modulation control signal, which is the output of the electronic circuit, is fed back to the laser diode 210.

The signal path from the laser diode 210 to the photodetector 250 via the 90% reflector 240 located at the receiving unit 300 side is opto-electronic feedback loop (i.e., long cavity) Thereby forming an optical path of the light. The photodetector 250, the electronic circuits 260 and 270, and the laser diode 210 also form the electron path of the opto-electronic feedback loop.

In order to be able to sustain the oscillation at the frequency selected by the RF filter 260, the overall loop gain of the opto-electronic feedback loop must be greater than the total loop loss. The total loop loss of the opto-electronic feedback loop occurs not only in optical fibers and light reflectors, but also in the process of converting an optical signal into an RF signal or changing an RF signal from a laser diode 210 to a light pulse. Therefore, in order to satisfy the oscillation condition, these losses must be compensated in the RF amplifier 270. [

In the upper optoelectronic feedback loop, the oscillation frequency is determined by the total length of the optical path including the optical fiber.

는 발진 주파수,

은 모드 수로서 임의의 정수,

는 매질 속 전자기파의 속도를 의미한다. 예컨대,

,

라면,

는 80 MHz가 된다. here,

The oscillation frequency,

Is an arbitrary integer as the number of modes,

Means the velocity of the electromagnetic wave in the medium. for example,

,

Ramen,

Is 80 MHz.

Since the optical-electronic feedback loop includes the transmission path fiber 400 as an optical path, the optical delay of the transmission path fiber 400 is changed by external environmental factors such as temperature, pressure, The overall loop delay will also change accordingly. This change in optical delay changes the oscillation frequency within the bandwidth of the band pass filter 260 of the electronic circuit. According to an embodiment of the present invention, since the transmitter 100 and the receiver 300 share one frequency on the opto-electronic feedback loop, the oscillation frequency is always changed even when the oscillation frequency is changed. That is, the transmitter 100 and the receiver 300, which are remotely located apart from each other, share the same oscillation frequency, regardless of changes in the external environmental factors applied to the transmission path fiber 400.

FIG. 3 is a diagram schematically showing a configuration of a transmission / reception system for synchronizing using a photoelectric oscillator according to another embodiment of the present invention.

The transmission line fiber 400 provides a very long optical path to the opto-electronic feedback loop (i.e., a long cavity), and in some cases, when the transmission line fiber 400 undergoes a significant length change, . In consideration of this, in another embodiment of the present invention, in addition to the opto-electronic feedback loop (i.e., the long cavity) including the transmission path fiber 400 as the optical path, a separate opto-electronic feedback loop path That is, a short cavity can be added in parallel to stabilize the oscillation frequency to a certain degree. 3 shows a short cavity including a short optical path 310 not passing through the transmission line fiber 400 and sharing a long cavity with the optical detector 250, the RF filter 260, and the RF amplifier 270. [ Are illustrated.

The foregoing description is merely illustrative of the technical idea of the present embodiment, and various modifications and changes may be made to those skilled in the art without departing from the essential characteristics of the embodiments. Therefore, the present embodiments are to be construed as illustrative rather than restrictive, and the scope of the technical idea of the present embodiment is not limited by these embodiments. The scope of protection of the present embodiment should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

100: Transmitter 210: Laser diode
220: 10% reflector 230: optical rotator
240: transmission line fiber 250: photo detector
260: RF filter 270: RF amplifier
310: Short sight

Claims (6)

A transmitting apparatus of a synchronous data communication system,
A laser that forms an optical oscillation in response to an electrical modulation control signal;
1. An opto-electronic feedback loop having a loop gain greater than one, the opto-electronic loop having a loop gain greater than one, An electro-optical loop for converting a signal into the modulation control signal related to the optical oscillation; And
Optic loop to obtain a part of the optical signal output by the laser, and a transmission section which uses the obtained optical signal as a carrier wave,
. The method according to claim 1,
The photo-
A light splitter for splitting the optical signal output from the laser into a first optical signal and a second optical signal;
A optical rotator optically connected to the optical splitter to transmit the first optical signal to the transmission line fiber and receive a reflection signal of the first optical signal received from the transmission line fiber;
A photodetector for detecting a reflected signal of the first optical signal; And
An electronic circuit for generating the modulation control signal from the output of the photodetector;
And a transmission unit for transmitting the transmission data. 3. The method of claim 2,
The electronic circuit includes:
A band pass filter for selecting a desired oscillation frequency of the laser; And
And an amplifier for amplifying the output of the band pass filter to generate the modulation control signal. The method according to claim 1,
The oscillation frequency of the laser is,

, ≪ / RTI >

The oscillation frequency,

Is an arbitrary integer as the number of modes,

Is a speed of an electromagnetic wave in the medium. The method according to claim 1,
A short optical path 310 not passing through the transmission path fiber 400 further comprises a second electro-optical loop optically connected in parallel with the electro-optical loop (hereinafter referred to as the first electro-optical loop) Optical path of the second electro-optical loop does not pass through the transmission path fiber. A synchronizing method of a transmitting apparatus and a receiving apparatus of a synchronous data communication system,
An optical-electronic feedback loop is formed for a laser which forms an optical oscillation, the optical-optical loop including a transmission fiber between the transmitting apparatus and the receiving apparatus as a part of an optical path, Wherein a part of the optical signal output by the laser is used as a carrier wave and the receiving device uses a part of the optical signal transmitted through the transmission path fiber as a carrier wave. How to synchronize.

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