KR102016928B1

KR102016928B1 - Method and Apparatus for Synchronizing using Opto-electronic Oscillator

Info

Publication number: KR102016928B1
Application number: KR1020140150110A
Authority: KR
Inventors: 김장면
Original assignee: 아이디 퀀티크 에스.에이.
Priority date: 2014-10-31
Filing date: 2014-10-31
Publication date: 2019-10-14
Also published as: KR20160050925A

Abstract

Disclosed are a transmission and reception synchronization method and apparatus using a photoelectric oscillator.
According to an aspect of the present embodiment, by using the optical fiber between the transmitter and the receiver as a resonator of the photoelectric oscillator, there is provided a transmission and reception synchronization method and apparatus in a manner that the transmitter and receiver share the oscillation frequency that changes depending on the disturbance, etc. applied to the optical fiber do.

Description

Transmission and reception synchronization method and apparatus using a photoelectric oscillator {Method and Apparatus for Synchronizing using Opto-electronic Oscillator}

The present embodiment relates to a transmission and reception synchronization method and apparatus using a photoelectric oscillator. More specifically, 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 according to disturbances or the like applied to an optical fiber by using an optical fiber between a transmitter and a receiver as a resonator of an optical oscillator.

The contents described in this section merely provide background information on the present embodiment and do not constitute a 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 the information sent by the transmitter over the channel. To do this, the receiver samples the input signal at the appropriate 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 a phase of an input signal using a clock recovery circuit such as a phase lock loop (PLL) in a 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 shift in the input data signal. In particular, the phase difference of the synchronization signal occurs due to the temperature change or mechanical vibration of the optical fiber in the long distance transmission. This causes a phase shift of the reproduction clock relative to the reference clock, increasing the probability of error occurrence. The phase change or phase change at a significant point in time of the data signal is called jitter. Jitter control is important because jitter degrades the performance of the transmission system and causes bit errors and uncontrolled slip on digital signals. Jitter causes bit errors by interrupting accurate sampling of digital signals by clock regeneration circuits. Effective management of jitter is important for creating systems with acceptable bit error rates.

In order to control this jitter, a technique of controlling jitter is mainly used by sending a part of a signal transmitted through an optical fiber at a receiver to sense noise of a fiber at the transmitter and compensate for it. The jitter control system in this manner is briefly shown in FIG.

The present embodiment uses a fiber between a transmitter and a receiver as a resonator of a photoelectric oscillator, thereby providing a transmission and reception synchronization method and apparatus in which a transmitter and a receiver share an oscillation frequency that changes according to disturbances applied to the optical fiber. There is this.

According to an aspect of the present embodiment, a transmission apparatus of a synchronous data communication system, comprising: a laser, which is included in an optoelectronic oscillator, and forms an optical oscillation in response to an electrical modulation control signal; An Opto-electronic Feedback Loop with a loop gain greater than 1, which transmits a portion of the optical signal output by the laser to a transmission fiber and reflects the light through the transmission fiber A first electro-optical loop for converting a signal into the modulation control signal related to the optical oscillation; A transmitter which is optically connected to the first electro-optic loop, obtains a part of the optical signal output by the laser, and uses the obtained optical signal as a carrier wave; And a second electro-optic loop optically connected in parallel with the first electro-optic loop, including a short optical path 310 not via the transmission fiber 400. The optical path of the loop provides a transmission device characterized in that it does not pass through the transmission fiber.

The optoelectronic oscillator includes: an optical splitter for dividing an optical signal output by the laser into a first optical signal and a second optical signal; An optical rotator optically coupled to the optical splitter, for transmitting the first optical signal to the transmission fiber and receiving a reflection signal of the first optical signal received from the transmission fiber; An optical detector 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 photo detector.

The electronic circuit includes a bandpass filter for selecting a desired oscillation frequency of the laser; And an amplifier for amplifying the output of the bandpass filter to generate the modulation control signal.

The oscillation frequency of the laser is It can be expressed as. Where Is the oscillation frequency, said Is a random integer as the number of modes, Is the speed of electromagnetic waves in the medium.

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According to another aspect of the present embodiment, in the method of synchronizing a transmitting device and a receiving device of a synchronous data communication system, a transmission fiber between the transmitting device and the receiving device is optically transmitted to a laser forming optical oscillation. The first electro-optic loop, including a short optical path 310 that forms a first Op-electronic feedback loop that includes as part of the path and does not pass through the transmission fiber 400. And further forming a second electro-optical loop that is optically connected in parallel, wherein the optical path of the second electro-optic loop does not pass through the transmission fiber and the transmitter transmits a portion of the optical signal output by the laser. It is used as a carrier, and the receiving device uses a portion of the optical signal transmitted through the transmission fiber as a carrier wave, characterized in that It provides a synchronization method of a transmitting apparatus and a receiving apparatus in a communication system.

As described above, according to the present embodiment, since the opto-electronic feedback loop includes the transmission fiber as the optical path, the optical delay of the transmission fiber due to external environmental factors such as temperature, pressure, etc. Even if the oscillation frequency of the opto-electronic feedback loop changes as the delay changes, the transmitter and the receiver sharing the oscillation frequency on the opto-electronic feedback loop share the same oscillation frequency.

1 is a view schematically showing a conventional jitter control system.
2 is a diagram schematically illustrating a configuration of a transmission / reception system for synchronizing using a photoelectric oscillator according to an embodiment of the present invention.
3 is a diagram schematically illustrating a configuration of a transmission and 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 through exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible even though they are shown in different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

In addition, in describing the component of this invention, terms, such as 1st, 2nd, A, B, (a), (b), can be used. These terms are only for distinguishing the components from other components, and the nature, order or order of the components are not limited by the terms. Throughout the specification, when a part is said to include, 'include' a certain component, which means that it may further include other components, except to exclude other components unless otherwise stated. . In addition, as described in the specification. The terms 'unit' and 'module' refer to a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software.

2 is a diagram schematically illustrating a configuration of a transmission / reception system for synchronizing using a photoelectric oscillator according to an embodiment of the present invention. As shown in FIG. 2, the transmitter 100 and the receiver 130 form an opto-electronic feedback loop (Opto-electronic Feedback Loop; Long Cavity) including a transmission fiber as an optical path. ) Is synchronized.

The optoelectronic oscillator includes a laser for generating pulsed light based on a modulation control signal. The laser may be a diode (Laser Diode) 210 in some embodiments, as illustrated in FIG. 2, a multi-mode solid state laser, a diode pump laser,

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

The pulsed light generated by the laser diode 210 meets the light splitter, a part of which is transmitted to the transmitter 100, and the other part of the pulsed light is transmitted to an optical circular 230. In FIG. 2, it is assumed that the 10% reflector 220 delivers 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, Port 3), and transmits the light received at the port 1 to the port 2, and transmits the light received at the port 2 to the 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. Port 2 is optically connected to transmission fiber 400 through fiber or free space to transfer input light from port 1 to transmission fiber 400, and reflected light received from transmission fiber 400 To port 2. Port 3 is optically connected to photodetector 250 via a fiber or free space to deliver the reflected light from port 2 to photodetector 250.

The input light transmitted from the port 1 of the optical rotator 230 to the transmission fiber 400 meets the optical splitter located at the reception side transmission fiber 400. In FIG. 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 photo detector 250 for detecting the reflected light received from the optical rotator, and an electronic circuit for generating a modulation control signal from the output of the photo detector 250. In the embodiment illustrated in FIG. 2, the electronic circuit amplifies the output of the RF filter (ie, bandpass filter 260) and the RF filter 260 to select a desired oscillation frequency to modulate the control signal of the laser diode 210. It consists of an RF amplifier 270 to generate a. The modulation control signal, which is the output of the electronic circuit, is fed back to the laser diode 210.

Thus, the signal path from the laser diode 210 to the photo detector 250 via the 90% reflector 240 located on the receiver 300 side is an opto-electronic feedback loop (ie, long cavity). To form an optical path. In addition, the photo detector 250, the electronic circuits (ie 260, 270) and the laser diode 210 form the electron path of the photo-electronic feedback loop.

In order to be able to continue oscillation at the frequency selected by the RF filter 260, the total 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 the optical fiber and the light reflector, but also in the process of converting the optical signal into the RF signal or the RF signal from the laser diode 210 to the optical pulse. Thus, to meet the oscillation condition, these losses must be compensated for in the RF amplifier 270.

In the above opto-electronic feedback loop, the oscillation frequency is determined by the total length Ltotal of the optical path including the optical fiber.

here, Is the oscillation frequency, Is the number of modes, any integer, Is the speed of electromagnetic waves in the medium. for example, , Ramen, Becomes 80 MHz.

Since the opto-electronic feedback loop includes the transmission fiber 400 as the optical path, the optical delay of the transmission fiber 400 changes due to external environmental factors such as temperature and pressure. The overall loop delay also changes. This change in the optical delay changes the oscillation frequency within the bandwidth of the bandpass 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 shared even if the oscillation frequency is changed. That is, despite the change in the external environmental factors applied to the transmission fiber 400, the transmitter 100 and the receiver 300 which are remotely separated from each other share the same oscillation frequency.

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

The transmission fiber 400 provides a very long optical path in the opto-electronic feedback loop (i.e., long cavity), and in some cases the oscillation frequency may change significantly accordingly if the transmission fiber 400 undergoes a severe length change. Can be. In view of this, in another embodiment of the present invention, in addition to the opto-electronic feedback loop (i.e., long cavity) that includes the transmission fiber 400 as the optical path, a shorter but more stable opto-electronic feedback loop path ( That is, by adding a short cavity in parallel, the stability of the oscillation frequency can be secured to a certain degree. 3 includes a short light path 310 which does not pass through the transmission fiber 400, but shares a long cavity with a photodetector 250, an RF filter 260, and an RF amplifier 270. Is illustrated.

The above description is merely illustrative of the technical idea of the present embodiment, and those skilled in the art to which the present embodiment belongs may make various modifications and changes without departing from the essential characteristics of the present embodiment. Therefore, the present embodiments are not intended to limit the technical idea of the present embodiment but to describe the present invention, 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 interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present embodiment.

100: transmitter 210: laser diode
220: 10% reflector 230: optical rotator
240: transmission path fiber 250: optical detector
260: RF filter 270: RF amplifier
310: Short Light Path

Claims

In the transmission apparatus of the synchronous data communication system,
A laser included in the optoelectronic oscillator, the laser forming an optical oscillation in response to the electrical modulation control signal;
An Opto-electronic Feedback Loop with a loop gain greater than 1, which transmits a portion of the optical signal output by the laser to a transmission fiber and reflects the light through the transmission fiber A first electro-optical loop for converting a signal into the modulation control signal related to the optical oscillation;
A transmitter which is optically connected to the first electro-optical loop, obtains a part of the optical signal output by the laser, and uses the obtained optical signal as a carrier wave; And
A second electro-optic loop optically connected in parallel with the first electro-optic loop, including a short optical path 310 that does not pass through the transmission fiber 400,
And wherein the optical path of the second electro-optical loop does not pass through the transmission fiber.

The method of claim 1,
The optoelectronic oscillator,
An optical splitter dividing the optical signal output by the laser into a first optical signal and a second optical signal;
An optical rotator optically coupled to the optical splitter, for transmitting the first optical signal to the transmission fiber and receiving a reflection signal of the first optical signal received from the transmission fiber;
An optical detector 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 photo detector
Transmission device comprising a.

The method of claim 2,
The electronic circuit,
A bandpass filter for selecting a desired oscillation frequency of the laser; And
And an amplifier for amplifying the output of the bandpass filter to generate the modulation control signal.

The method of claim 1,
The oscillation frequency of the laser is,
Expressed as above Is the oscillation frequency, said Is a random integer as the number of modes, Ltotal is the total length of the optical path, Is a speed of electromagnetic waves in the medium.

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A synchronization method of a transmitting device and a receiving device of a synchronous data communication system,
For a laser forming an optical oscillation, a first Opto-electronic feedback loop is formed comprising a transmission fiber as part of an optical path between the transmitter and the receiver, and the transmission A second electro-optical loop further optically connected in parallel with the first electro-optic loop, including a short optical path 310 that does not pass through the raw fiber 400, wherein the second electro-optic loop The optical path does not pass through the transmission fiber,
The transmitter uses a portion of an optical signal output from the laser as a carrier, and the receiver uses a portion of an optical signal transmitted through a transmission fiber as a carrier. And a synchronization method of the receiving device.