KR20170077415A - Apparatus and method for receiving optical coherent - Google Patents

Abstract

Receiving a first optical signal including an optical carrier including a pilot tone signal, receiving a second optical signal including a light source, combining the first optical signal and the second optical signal to generate a third optical signal, The present invention provides an optical coherent receiving apparatus and method for estimating a distorted tone signal generated from a third optical signal and comparing and analyzing a pilot tone signal and a distorted tone signal to compensate for frequency offset and phase noise for the third optical signal do.

Description

 [0001] APPARATUS AND METHOD FOR RECEIVING OPTICAL COHERENT [0002]

The present invention relates to an optical coherent receiving apparatus and method.

Carrier frequency offset (CFO) due to the frequency fluctuation and phase difference of the two components in the process of photoelectrically converting the optical carrier wave modulated by the optical coherent system and the optical local oscillator at the receiving end together through the photodiode, Problems and phase noise (PN) problems may occur.

Since these components have the property of random variable over time, accurate line estimation is impossible and compensation process after receiving is necessary.

(Patent Literature) Korean Patent Publication No. 2012-0068337

(Patent Literature) Korean Published Patent Application No. 2003-0065082

An embodiment of the present invention aims at compensating for a frequency offset and a phase distortion phenomenon by using a carrier wave including a pilot tone signal.

The optical coherent receiver according to an exemplary embodiment of the present invention includes an optical carrier receiver that receives a first optical signal including an optical carrier including a pilot tone signal, a local oscillator that generates a second optical signal including a light source, An optical hybrid for combining the first optical signal and the second optical signal to generate a third optical signal, a tone estimator for estimating a distorted tone signal generated from the third optical signal, And a signal compensator for comparing and analyzing the distorted tone signal to compensate for frequency offset and phase noise for the third optical signal.

According to an aspect of the present invention, the optical hybrid can generate the third optical signal without using a carrier suppression technique.

According to an aspect of the present invention, the signal compensator may calculate and compensate the phase noise by dividing the pilot tone signal component for each frame of the third optical signal.

According to an aspect of the present invention, the signal compensator may compensate for the frequency offset phenomenon by shifting a tone by the pilot tone signal component with respect to the entire band of the third optical signal.

The optical coherent reception method according to an embodiment of the present invention includes the steps of receiving a first optical signal including an optical carrier including a pilot tone signal, outputting a second optical signal including a light source, The method includes the steps of generating a third optical signal by combining the optical signal and the second optical signal, estimating a distorted tone signal generated from the third optical signal, and comparing and analyzing the pilot tone signal and the distorted tone signal , And compensating for frequency offset and phase noise for the third optical signal.

According to an aspect of the present invention, the step of generating the third optical signal may include the step of generating the third optical signal without using a carrier suppression technique.

According to an aspect of the present invention, the step of compensating the frequency offset and the phase noise for the third optical signal includes: dividing the pilot tone signal component for each frame of the third optical signal, .

According to an aspect of the present invention, the step of compensating the frequency offset and the phase noise for the third optical signal may include shifting a tone by the pilot tone signal component with respect to the entire band of the third optical signal, Compensating step.

According to an embodiment of the present invention, a frequency offset and a phase distortion phenomenon can be compensated using a carrier wave including a pilot tone signal.

1 is a block diagram showing the configuration of a coherent receiving apparatus according to an embodiment of the present invention.
2 is a diagram illustrating a process of generating a third optical signal in an optical hybrid according to an embodiment of the present invention.
3 is a diagram illustrating a process of restoring an optical signal by comparing pilot tones according to an embodiment of the present invention.
4 is a diagram illustrating a method of optical coherent reception according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention will now be described in detail with reference to the accompanying drawings and the accompanying drawings, wherein specific structural or functional descriptions for embodiments according to the concepts of the present invention disclosed herein The embodiments according to the concept of the present invention may be embodied in various forms and are not limited to the embodiments described herein.

Embodiments in accordance with the concepts of the present invention are capable of various modifications and may take various forms, so that the embodiments are illustrated in the drawings and described in detail herein. It is to be understood, however, that the intention is not to limit the embodiments according to the concepts of the present invention to the specific disclosed embodiments, but includes modifications, equivalents, or alternatives falling within the spirit and scope of the present invention

The terms first, second, or the like may be used to describe various elements, but the elements should not be limited by the terms. The terms may be named for the purpose of distinguishing one element from another, for example without departing from the scope of the right according to the concept of the present invention, the first element being referred to as the second element, Similarly, the second component may also be referred to as the first component.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between. Expressions that describe the relationship between components, for example, "between" and "immediately" or "directly adjacent to" should be interpreted as well.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises ", or" having ", and the like, are used to specify one or more of the features, numbers, steps, operations, elements, But do not preclude the presence or addition of steps, operations, elements, parts, or combinations thereof.

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. The terminology used herein is a term used for appropriately expressing an embodiment of the present invention, which may vary depending on the user, the intent of the operator, or the practice of the field to which the present invention belongs. Therefore, the definitions of these terms should be based on the contents throughout this specification.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this embodiment belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as ideal or overly formal in the sense of the art unless explicitly defined herein Do not.

In the following description of the present invention with reference to the accompanying drawings, the same components are denoted by the same reference numerals regardless of the reference numerals, and redundant explanations thereof will be omitted. In the following description of the embodiments, a detailed description of related arts will be omitted if it is determined that the gist of the embodiments may be unnecessarily blurred.

It is possible to photoelectrically convert the optical carrier wave whose signal is modulated in the optical coherent system and the optical local oscillator at the receiving end via the photodiode. An optical signal modulated using a general IQ (In-phase and quadrature) modulator can be expressed by Equation (1) below.

[Equation 1]

는 광 IQ 변조기에서 변조된 광신호의 전기장이고,

는 광 IQ 변조기로 들어가는 레이저 광원의 전기장이고,

는 각각 광 IQ 변조기의 In-phase 성분과 Quadrature 성분을 변조하는 과정에 의한 위상 천이 정도를 의미한다. here,

Is the electric field of the optical signal modulated in the optical IQ modulator,

Is the electric field of the laser light source entering the optical IQ modulator,

Denotes the degree of phase shift due to the process of modulating the In-phase component and the Quadrature component of the optical IQ modulator, respectively.

In a coherent system, a receiver can receive an optical signal using a local oscillator. In a coherent receiver, the sum of the electric field due to the two lights is detected. Since the optical output is the square of the electric field, Can be expressed by Equation (2).

&Quot; (2) "

는 광 국부 발진기에서 발생된 광원의 전기장의 켤레 복소수값을 의미하고,

는 광 신호 반송파와 광 국부 발진기에서 발생된 광원 사이의 주파수 오프셋을 의미하고

는 광 신호 반송파와 광 국부 발진기에서 발생된 광원 사이의 위상차로 인한 위상잡음 성분을 의미한다. 실제 레이저 광원은 단색광이 아니기 때문에 반송파 주파수 오프셋이 존재하고, 서로 다른 광원이기 때문에 위상 차이로 인한 위상 잡음이 존재할 수 있다. 이러한 위상 차이로 인한 위상 잡음 성분은 상기 수학식 2와 같이 검출된 신호 값에 직접적으로 영향을 주기 때문에 보상이 필요하다.here

Quot; denotes the complex conjugate value of the electric field of the light source generated in the optical local oscillator,

Denotes the frequency offset between the optical signal carrier and the light source generated in the optical local oscillator

Denotes a phase noise component due to a phase difference between an optical signal carrier and a light source generated in the optical local oscillator. Since the actual laser light source is not a monochromatic light, there is a carrier frequency offset, and since it is a different light source, phase noise due to phase difference may exist. Since the phase noise component due to the phase difference directly affects the detected signal value as shown in Equation (2), compensation is required.

Carrier frequency offset and phase noise are generated by the optical carrier on which the signal is placed and the light source on the local oscillator, so they are affected equally regardless of the type of RF signal.

In the optical coherent receiving apparatus according to an embodiment of the present invention, when transmitting a pilot tone signal to an optical carrier, the carrier coherent receiver compensates for the carrier frequency offset and phase noise by changing the frequency and phase of the pilot tone signal of the received optical carrier. can do.

For example, an optical coherent receiver according to an embodiment of the present invention compares an optical signal generated by combining an optical carrier and a light source, which are transmitted with a pilot tone signal, to a pilot tone signal and an estimated distortion tone signal, can do.

Hereinafter, a configuration of a coherent receiving apparatus according to an embodiment of the present invention will be described.

1 is a block diagram showing the configuration of a coherent receiving apparatus according to an embodiment of the present invention.

1, an optical coherent receiver according to an embodiment of the present invention includes an optical carrier receiver 110, a local oscillator 120, an optical hybrid 130, a tone estimator 160, And a compensation unit 170.

The optical carrier receiver 110 receives a first optical signal consisting of an optical carrier including a pilot tone signal.

The optical local oscillator 120 mixes the first optical signal and outputs a second optical signal corresponding to a kind of light source for generating an intermediate frequency.

The optical hybrid 130 combines the first optical signal and the second optical signal to generate a third optical signal.

The optical hybrid 130 combines the first optical signal input from the optical carrier receiver 110 and the second optical signal input from the optical local oscillator 120 and then outputs the combined third optical signal to the In- ) Channel component and a quadrature phase channel component.

When the input first optical signal is polarization multiplexed in the optical carrier receiver 110, the optical hybrid 130 converts the combined third optical signal into a positive phase channel component and a quadrature phase channel component in which x polarization and y polarization are mixed Can be separated.

The optical hybrid 130 may generate the third optical signal without using a carrier suppression technique.

2 is a diagram illustrating a process of generating a third optical signal in an optical hybrid according to an embodiment of the present invention.

1 and 2, an optical hybrid 130 combines a first optical signal 210 and a second optical signal 220, which are optical carriers including a pilot tone signal, to form a third optical signal 230, Lt; / RTI >

Referring again to FIG. 1, the optical coherent receiving apparatus according to an aspect of the present invention may further include a photoelectric converter 140, and an ADC 150.

The photoelectric converter 140 may convert an optical signal input from the optical hybrid 320 into an electrical signal.

The ADC 150 may convert an electrical signal input from the photoelectric converter 140 into a digital signal.

The tone estimator 160 estimates a distortion tone signal generated from the third optical signal.

The tone estimator 160 detects a distorted tone signal caused by the interference between the optical carrier receiver 110 component and the optical local oscillator 120 component when performing optical modulation without using a carrier suppression technique, can do.

The signal compensator 170 compares and analyzes the pilot tone signal and the distortion tone signal to compensate for the frequency offset and the phase noise for the third optical signal.

According to an aspect of the present invention, since the carrier frequency offset and the phase noise estimated for the distorted tone signal appear uniformly over all frequency bands, when the carrier frequency offset and the phase noise calculation result are inversely calculated, the overall distortion of the optical signal is compensated can do.

The signal compensator 170 receives the optical carrier signal including the pilot tone signal and compares the distortion of the distortion tone signal with respect to the pilot tone signal to analyze the influence of the overall carrier frequency offset and the phase noise.

3 is a diagram illustrating a process of restoring an optical signal by comparing pilot tones according to an embodiment of the present invention.

1 and 3, the signal compensator 170 extracts a pilot tone signal component 320 from the first optical signal 310 and outputs a pilot tone signal component 320 for each frame of the third optical signal 330. [ (320), thereby estimating and compensating for the phase noise.

가 곱해진 형태로 영향이 나타나기 때문에, 신호 보상부(170)는 송신 당시의 위상과 동일하도록 파일럿 톤 신호 성분(320)을 전체 광 신호에 나누어 주면 위상 잡음을 추정해 보상할 수 있다(340).For example, the phase noise effect for each frame is given by

The signal compensator 170 can estimate and compensate for the phase noise by dividing the pilot signal component 320 into the entire optical signal so that the phase is equal to the phase at the time of transmission 340. [ .

The signal compensating unit 170 can compensate for the frequency offset phenomenon by shifting the tone of the pilot tone signal component with respect to the entire band of the third optical signal.

For example, since the influence of the carrier frequency offset is represented by the movement of the tone, the signal compensator 170 can compensate for the entire band of the optical signal by shifting it by the pilot tone signal component.

Hereinafter, an optical coherent reception method according to an embodiment of the present invention will be described. The optical coherent receiving method according to an embodiment of the present invention can be performed using the optical coherent receiving apparatus described above, and the optical coherent receiving apparatus will be mainly described.

4 is a diagram illustrating a method of optical coherent reception according to an embodiment of the present invention.

Referring to FIG. 4, the optical coherent receiver receives a first optical signal including an optical carrier including a pilot tone signal (410).

The optical coherent receiving apparatus outputs a second optical signal including a light source (420).

The optical coherent receiver combines the first optical signal and the second optical signal to generate a third optical signal (430).

For example, the optical coherent receiver can generate a third optical signal without using a carrier suppression technique.

The optical coherent receiver estimates a distorted tone signal generated from the third optical signal (440).

The optical coherent receiver compares and analyzes the pilot tone signal and the distorted tone signal to compensate for the frequency offset and phase noise for the third optical signal (450).

The optical coherent receiving apparatus can calculate and compensate for the phase noise by dividing the pilot tone signal component for each frame of the third optical signal.

The optical coherent receiver can compensate for the frequency offset phenomenon by shifting the tone of the pilot tone signal component with respect to the entire band of the third optical signal.

 The apparatus described above may be implemented as a hardware component, a software component, and / or a combination of hardware components and software components. For example, the apparatus and components described in the embodiments may be implemented within a computer system, such as, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA) , A programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to execution of the software. For ease of understanding, the processing apparatus may be described as being used singly, but those skilled in the art will recognize that the processing apparatus may have a plurality of processing elements and / As shown in FIG. For example, the processing unit may comprise a plurality of processors or one processor and one controller. Other processing configurations are also possible, such as a parallel processor.

 The software may include a computer program, code, instructions, or a combination of one or more of the foregoing, and may be configured to configure the processing device to operate as desired or to process it collectively or collectively Device can be commanded. The software and / or data may be in the form of any type of machine, component, physical device, virtual equipment, computer storage media, or device , Or may be permanently or temporarily embodied in a transmitted signal wave. The software may be distributed over a networked computer system and stored or executed in a distributed manner. The software and data may be stored on one or more computer readable recording media.

 The method according to an embodiment may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions to be recorded on the medium may be those specially designed and configured for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

 While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents, even if it is replaced or replaced.

 Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

110: Optical Carrier Receiver
120: optical local oscillator
130: Optical hybrid
140: photoelectric converter
150: ADC
160:
170: Signal Compensation Unit

Claims (9)

An optical carrier receiver for receiving a first optical signal comprising an optical carrier comprising a pilot tone signal;
A light local oscillator for outputting a second optical signal including a light source;
An optical hybrid for combining the first optical signal and the second optical signal to generate a third optical signal;
A tone estimator for estimating a distortion tone signal generated from the third optical signal; And
A signal compensator for comparing and analyzing the pilot tone signal and the distortion tone signal to compensate for frequency offset and phase noise for the third optical signal,
And the optical coherent receiving device. The method according to claim 1,
In the optical hybrid,
A method of generating a third optical signal without using a carrier suppression technique,
Optical coherent receiver. The method according to claim 1,
Wherein the signal compensator comprises:
Estimating and compensating for the phase noise by dividing the pilot tone signal component for each frame of the third optical signal,
Optical coherent receiver. The method according to claim 1,
Wherein the signal compensator comprises:
And compensating for the frequency offset phenomenon by shifting a tone by the pilot tone signal component with respect to the entire band of the third optical signal,
Optical coherent receiver. Receiving a first optical signal comprising an optical carrier comprising a pilot tone signal;
Outputting a second optical signal including a light source;
Combining the first optical signal and the second optical signal to generate a third optical signal;
Estimating a distorted tone signal generated from the third optical signal; And
Comparing the pilot tone signal and the distortion tone signal to compensate for frequency offset and phase noise for the third optical signal,
/ RTI > 6. The method of claim 5,
Wherein the step of generating the third optical signal comprises:
Generating the third optical signal without using a carrier suppression technique;
/ RTI > 6. The method of claim 5,
Wherein compensating for frequency offset and phase noise for the third optical signal comprises:
Estimating and compensating for the phase noise by dividing the pilot tone signal component for each frame of the third optical signal,
/ RTI > 6. The method of claim 5,
Wherein compensating for frequency offset and phase noise for the third optical signal comprises:
Compensating for the frequency offset phenomenon by shifting a tone by the pilot tone signal component with respect to the entire band of the third optical signal,
/ RTI > 9. A computer-readable recording medium on which a program for performing the method of any one of claims 5 to 8 is recorded.

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