KR100831349B1 - Encoder and decoder of optical code devision multiple access using propagation constant - Google Patents

Abstract

An optical CDMA encoder and decoder using a propagation constant are provided to increase the width of an optical waveguide and remove components required to perform time delay, thereby delaying the proceeding speed and time of an incident optical signal in the encoder and the decoder and facilitating the miniaturization and integration of the encoder and the decoder. An optical CDMA(Code Division Multiple Access) encoder delays and forms transmission data converted into an optical signal on an optical waveguide according to a predetermined time code and a wavelength code and encrypts the transmission data. An optical CDMA decoder corresponds to the optical CDMA encoder to decode the encrypted optical signal. At least one time delay unit is formed on the optical waveguide formed in a first width(Wa) to delay the speed and time of the optical signal and is formed in a second width(Wb) wider than the first width. A mode adaptor is formed to combine the optical combination of a heterogeneous optical waveguide in a boundary between the time delay unit and the optical waveguide.

Description

Encoder and Decoder of Optical Code Devision Multiple Access Using Propagation Constant

1 is a block diagram schematically showing an optical CDMA system using a propagation constant according to the present invention.

2 is a conceptual diagram schematically illustrating an operation of an optical CDMA encoder using a time division propagation constant according to the present invention.

3 is a partially enlarged view for illustrating a time delay of an optical waveguide encoder using a propagation constant according to the present invention, which is part A of FIG.

4 is a conceptual diagram schematically showing an operation of an optical CDMA decoder using a time division scheme propagation constant according to the present invention.

5 is a partially enlarged view for illustrating a time delay of an optical waveguide decoder using a propagation constant according to the present invention, which is a portion B of FIG.

<Description of reference numerals for the main parts of the drawings>

1: optical CDMA system 20: optical transmitter

20a: light source 20b: encoder

20b ': Time delay 20c', 20c '': Mode adapter

40: optical receiver 40a: decoder

40a ': time delay 40b', 40b '': time delay

The present invention relates to an optical CDMA encoder and decoder using a propagation constant, and more particularly, by increasing the width of an optical waveguide for changing the propagation constant by using an optical speed that is changed according to the propagation constant in the optical CDMA. It is possible to delay the advancing speed and time of the incident optical signal of the encoder and the decoder which encrypts and decrypts the transmission data and the receiving data, and by increasing the number of time delay parts which increased the width of the optical waveguide, The present invention relates to an optical CDMA encoder and decoder using a propagation constant that is easy to miniaturize and integrate an encoder and a decoder because a proportional digital time delay can be obtained and components required for the time delay of the encoder and decoder system can be removed. .

In general, Optical Code Division Multiple Access (hereinafter referred to as optical CDMA) allows for multiple access by code or asynchronous connection between users, so that optical LAN, optical exchange, subscriber network and station transmission, and infrared It is available in the field of wireless communication and the like, and provides a switching function different from the wireless communication in the entire system including a transmitter and a receiver by random access and self-routing by code in a spread spectrum region.

In addition, the optical CDMA spreads a band by a time or a wavelength, encrypts a signal, and receives and restores the signal. In the case of encrypting a signal by temporally dividing the signal, the optical CDMA has a separate optical path difference for each signal for time division and delay. Create a time delay.

However, when optical CDMA divides and encrypts an optical signal in time, separate optical path differences are generated in a transmitter and a receiver of the optical CDMA system for temporal division and delay, so that an encoder of a transmitter and a decoder of a receiver are used. (Decoder) has increased in size, and thus, integration and miniaturization are not easy, and additional costs are increased by generating a separate optical path difference.

The present invention has been made to solve the above problems, by increasing the width of the optical waveguide for changing the propagation constant by using the optical speed that is changed according to the propagation constant in the optical CDMA, thereby transmitting and receiving data of the transmitter and receiver Digital time proportional to the time delay of a single optical waveguide by delaying the speed and time of the incident optical signal of the encoder and decoder to encrypt and decrypt, and by increasing the number of time delays that increased the width of the optical waveguide. It is an object of the present invention to provide an optical CDMA encoder and decoder using a propagation constant that is easy to miniaturize and integrate the encoder and decoder since delay can be obtained and components required for time delay of the encoder and decoder system can be eliminated.

In order to achieve the above object, the present invention provides an optical CDMA encoder for delaying and forming a transmission data converted into an optical signal in an optical waveguide according to a predetermined time code and a wavelength code; An optical CDMA decoder configured to correspond to the encoder to decrypt the encrypted optical signal; A time delay unit configured to increase a width of a portion of the optical waveguide to generate a speed and a time delay of the optical signal in the optical waveguides of the encoder and the decoder; A mode adapter for optical coupling of heterogeneous waveguides to a boundary between the time delay unit and the optical waveguide; Included.

The speed and time delay of the optical signal may be proportional to the width of the time delay unit.

The speed and time delay of the optical signal may be proportional to the length of the time delay unit.

The speed and time delay of the optical signal is proportional to the number of time delay units.

A mode adapter for optical coupling of heterogeneous waveguides to a boundary between the time delay unit and the optical waveguide; It characterized in that it further comprises.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram schematically showing an optical CDMA system using a propagation constant according to the present invention. As shown in the figure, the optical network composed of the optical CDMA system 1 converts the data to be transmitted to the light source 20a, and encodes and transmits the encoder 20b for encoding and transmitting the light output from the light source 20a. And a combiner (not shown) for distributing the encoded optical signals received from the plurality of optical transmitters 20, a decoder 40a for decoding the received optical signals, and the optical transmitter ( And an optical receiver 40 including a determiner (not shown) for determining whether or not the data has been transmitted at 20).

Each subscriber of the optical network is connected to one optical transmitter 20 and an optical receiver 40, and each optical transmitter 20 or each optical receiver 40 is identified by a specific code. The optical transmitter 20 has a variable encoder 20b capable of producing optical signals that conform to this particular code, and the optical receiver 40 includes a fixed decoder 40a to receive only optical signals that conform to this code. Equipped.

In addition, the optical transmitter 20 includes optical signals that are encoded according to the type of the bits of the destination optical receiver 40 in the data bits to be sent through the encoder 20b, and combines at the center of the optical network ( Transmits to all optical receivers 40 through a not shown.

At this time, the optical signal is decoded by the decoder 40a in each of the optical receivers 40. In the optical receiver 40 as a destination, an optical signal having an intensity greater than or equal to a threshold value is detected, and other optical signals are detected. The receiver 40 receives data bits in such a manner that an optical signal having an intensity less than or equal to a threshold value is detected.

FIG. 2 is a conceptual diagram schematically illustrating the operation of an optical CDMA encoder using a time division propagation constant according to the present invention, and will be described with reference to FIG. 1. As shown in the figure, the data to be transmitted is changed to the light source 20a, and the light source 20a is incident on the encoder 20b of the transmitter, which is called an optical signal.

A method of dividing the incident optical signal into N pieces, delaying each power at a predetermined time interval (Time Delay), distributing them at regular time intervals, and encrypting time is illustrated.

Here, the incident optical signal is divided into N through 1 XN splitters, and each divided optical signal has a time delay of a predetermined time interval with respect to time. The first optical signal A divided into N is A Part (a) proceeds without any time delay.

In addition, the second optical signal divided by N and (B) of the A part, which is divided into N, has a time delay (Δt) shown in a circle, and the circle generally has a time delay ( Time Delay).

The optical signal having a time delay equal to the number of circular circles proceeds with a time delay Δt than the optical signal of (a).

In addition, (C) of the A portion, which is the third optical signal divided into N, after passing through the 1 XN splitter, has two time delays (2 · Δt) shown in two circles, and ( It has a time delay of Δt over the optical signal of b) and a time delay of 2 · Δt over the optical signal of (a).

In addition, (D) of the A portion, which is the N-th optical signal divided into N, is passed through the 1 XN splitter, and N-1 time delays (N-1 · Δt) shown by N-1 circles. ), Has a time delay of (N-3) · Δt than the optical signal of (C), and has a time delay of (N-2) · Δt than the optical signal of (B). In addition, the optical signal of (a) has a time delay of (N−1) · Δt.

FIG. 3 is a partially enlarged view for illustrating a time delay of the optical waveguide encoder 20b using the propagation constant according to the present invention, which is part A of FIG. 2, and will be described with reference to FIG. 1. As shown in the figure, to adjust the width of the waveguide in the encoder 20b for the time delay of the incident N optical signals separated into pieces, by adjusting the width, the propagation constant can be changed, and thus the optical speed. Because it can change.

This is as follows.

V _g = dω / dβ

The speed of light traveling through the optical waveguide may be expressed as a group velocity (V _g ), where ω is a frequency and β is a propagation constant.

And, in order to control the group speed, the frequency or propagation constant must be converted. The propagation constant can be adjusted by converting a variable such as the width or wavelength of the optical waveguide or the refractive index of the material.

In addition, since the wavelength is determined when transmitting an optical signal containing data, and the refractive index of the material is determined before the design of the optical waveguide, the optical velocity of each optical waveguide must be changed in order to change the propagation constant. Can vary and cause time delays.

At this time, the time delay of the optical speed traveling through the optical waveguide is non-linearly proportional to the width of the optical waveguide.

Here, the incident optical signal is divided into N through 1 XN splitters, and each divided optical signal has a time delay of a predetermined time interval with respect to time, which is the first optical signal divided into N ( A) proceeds without any time delay, and thus does not change the optical waveguide, and the width of the optical waveguide is Wa.

In addition, since the second optical signal divided by N and (I) having a 1 XN splitter has a time delay (Δt) shown in a circle, it is possible to change the propagation constant that can change the speed of light. To produce a time delay 20b ₁ ′ for delaying the time, the width of the optical waveguide is increased from Wa to Wb, and the length is defined as ΔL.

The optical signal having the time delay of the single time delay unit 20b ₁ ′ has a time delay of Δt than the optical signal of (a).

Here, since a transmission loss may occur between the optical waveguide having a width of Wa and the time delay portion 20b ₁ ′, which is an optical waveguide having a width of Wb, a mode adapter (B) may be provided at both sides of the time delay portion 20b ₁ ′. Mode Adapoter, 20c ₁ ′, 20c ₁ ″).

In addition, the third optical signal (C), which is divided into N and passes through the 1 XN splitter, has two time delays (2 · Δt) shown in two circles. It has a time delay of Δt than the optical signal, and a time delay of 2 · Δt than the optical signal of (a).

Here, two time delay units 20b ₁ ′ and 20b ₂ ′ are formed in the optical waveguide to change the propagation constants so as to cause an optical signal to have a time delay of 2 · Δt.

In this case, since the transmission loss between the optical waveguide having a width of Wa and the time delay portions 20b ₁ ′ and 20b ₂ ′, which is an optical waveguide having a width of Wb, may occur, the time delay units 20b ₁ ′ and 20b ₂ may occur. Mode adapters 20c ₁ ′, 20c ₁ ″, 20c ₂ ′, and 20c ₂ ″ are provided on both sides of the ').

In addition, after the 1 XN splitter, the N-th optical signal divided into N (D) is N -1 circular and time delay units 20b ₁ ', 20b ₂ ', 20b ₃ ', ... Nb has one time delay (N−1 · Δt), shown as 20b _{N −1} ′), and has a time delay of (N−3) · Δt over the optical signal of (C), It has a time delay of (N−2) · Δt than the optical signal of (b) and a time delay of (N−1) · Δt than the optical signal of (a).

At this time, the time delay unit 20b ₁ ', 20b ₂ ', 20b ₃ ', ... 20b _{N -1} ' is formed in the optical waveguide N-1 at a predetermined interval to form an optical signal N-1 · △ Change the propagation constant to cause a time delay of t.

Here, the width Wb of the optical waveguide on which the time delay parts 20b ₁ ', 20b ₂ ', 20b ₃ ', ... 20b _{N -1} ' are formed is different from the conventional optical waveguide width Wa, The mode that the call guides may vary, and thus, a mode adapter is further included for optical coupling between heterogeneous waveguides.

In this case, transmission loss between the optical waveguide having a width of Wa and the time delay units 20b ₁ ′, 20b ₂ ′, 20b ₃ ′, ‥‥ 20b _{N −1} ′, which are optical waveguides having a width of Wa, may occur. Therefore, the mode adapter (20c ₁ ', 20c ₁ ', 20c ₁ ', 20c ₂ ' on both sides of each of the time delay unit (20b ₁ ', 20b ₂ ', 20b ₃ ', ... 20b _{N- 1} ') , and a _{20c 2 '', 20c 3 '} , 20c 3'', ‥‥ 20c N -1', 20c N-1 '').

4 is a conceptual diagram schematically illustrating an operation of an optical CDMA decoder using a time division scheme propagation constant according to the present invention, and will be described with reference to FIG. 1. As shown in the figure, an optical signal according to a time delay, which is received data, is incident to the decoder 40a of the optical receiver 40.

In the encoding of the encoder 20b, which is an encryption process of the optical transmitter 20, each power is delayed at a predetermined time interval, and at the same time, the optical signal encrypted with respect to time passes through a 1 × N splitter. do.

Then, a part A of the first optical signal divided into N parts of the optical transmitter 20 through 1 x N splitters is equal to (A) of part A of the Nth optical signal. -1) Since there is a time delay of △ t, to compensate for the time delay of (N-1) do.

In addition, the (I) of the second part of the A signal divided into N of the optical transmitter 20 through 1 x N splitter (B) is less than the (D) of the A part of the Nth optical signal. 2) Since Δt has a time delay, to compensate for the delay of (N-2) Δt, a time delay of (N-2) Δt is given to (b) of B. .

After passing through a 1 x N splitter, (C) of part A, which is the third signal divided into N pieces of the optical transmitter 20, (C) is smaller than (D) of part A of the Nth optical signal. 3) Since the time delay is as much as Δt, the time delay of (N-3) and Δt is given to (C) of B to compensate for the time delay by (N-3) and Δt. .

Finally, (D) of the A portion, which is the Nth signal divided into N of the optical transmitter 20 through 1 x N splitters, is an Nth optical signal, and thus has no time delay. Decrypted.

As described above, the optical transmitter 20 compensates for the optical signal given a time delay, and compensates the optical signal for which the time delay is not applied. The signal is combined and decoded into one, and includes the noise according to decoding when the signal is decoded.

FIG. 5 is a partially enlarged view for illustrating a time delay of an optical waveguide decoder according to the present invention, which is part B of FIG. 4. It demonstrates with reference to FIG. As shown in the figure, an optical signal that is data that has been separated at a predetermined interval (Δt) with respect to the time incident to the optical receiver 40 passes through a splitter of 1 x N, respectively divided optical signal Since part (a) of part A did not have any time delay with respect to a time delay of a predetermined time interval, the time delay part 40a ₁ by (N-1) .Δt in part (a) of part B. ', 40a ₂ ', 40a ₃ ', ..., 40a _{N -1} ', wherein the time delay (40a ₁ ', 40a ₂ ', 40a ₃ ', ..., 40a _N-1 ') N-1 is formed, the width is Wb increased than the existing width Wa, and the length is formed as ΔL.

At this time, a transmission loss occurs between the optical waveguide having a width of Wa and each of the time delay parts 40a ₁ ′, 40a ₂ ′, 40a ₃ ′, ..., 40a _{N −1} ′, which are optical waveguides having a width of Wb. Since the time delays 40a ₁ ′, 40a ₂ ′, 40a ₃ ′, ..., 40a _{N −1} ′ may be used, mode adapters 40b ₁ ′, 40b ₁ '', 40b ₂ '' and a ', 40b _2' ', 40b _3', 40b ₃ '' ‥‥, 40b _{-1 N} ', _{N -1} 40b'').

In addition, part (A) of part A, which is the second optical signal divided into N parts, passes through the 1 x N splitter and has a time delay of Δt. 2) generate time delay parts 40a ₁ ′, 40a ₂ ′, 40a ₃ ′,..., 40a _{N − 2} ′ as much as Δt, where the time delay parts are formed with N − 2, With Wb increased from the existing width Wa, the length is formed to be ΔL, which is compensated by Δt over the (a) optical signal of the portion B and proceeds.

At this time, a transmission loss occurs between the optical waveguide having a width of Wa and the respective time delay parts 40a ₁ ′, 40a ₂ ′, 40a ₃ ′,..., 40a _{N −2} ′, which are optical waveguides having a width of Wb. number, each of the time delay unit, so _{(40a 1 ', 40a 2'} , 40a 3 ', ‥‥, 40a N -2') on both sides in the adapter mode (mode of _{Adapoter, 40b 1 ', 40b 1'} ', 40b 2 and a _{') -', 40b 2 '} ', 40b 3 ', 40b 3''‥‥, 40b N -2' 2, 40b N '.

After the 1 x N splitter, (C) of the A portion, which is the second optical signal divided into N, has two time delay parts 20b ₁ ′, 20b ₂ ′, and 2 · Δt As time delay is achieved, the time delay portion (40a ₁ ', 40a ₂ ', 40a ₃ ', ..., 40a _N-3 ') of (B) to (N-3). Wherein the time delay parts 40a ₁ ′, 40a ₂ ′, 40a ₃ ′,..., 40a _{N − 3} ′ are formed in N − 3, and the width is increased by more than the existing width Wa. Therefore, the length is formed to be ΔL, and the length is compensated by Δt from the optical signal of (b) of the B part to be advanced.

At this time, a transmission loss occurs between the optical waveguide having a width of Wa and the respective time delay parts 40a ₁ ′, 40a ₂ ′, 40a ₃ ′,..., 40a _{N −3} ′, which are optical waveguides having a width of Wb. Since the time delays 40a ₁ ′, 40a ₂ ′, 40a ₃ ′, ..., 40a _{N −3} ′ may be used, mode adapters 40b ₁ ′, 40b ₁ '', 40b ₂ '' and a _{', 40b 2'', 40b} 3', 40b 3 '' ‥‥, 40b N -3 ', 40b N -3'').

In addition, (D) of the A portion, which is the second optical signal divided into N, after passing through the 1 x N splitter, N−1 time delay units 20b ₁ ′, 20b ₂ ′, 20b ₃ ′, ‥ ..., 20b _{N -1} '), and has a time delay of (N-1) · Δt, so that the time delay portion 40a is not formed so as not to have any time delay in (D) of the B part. The optical waveguide is formed as it is, the width Wa of the existing optical waveguide.

As described above, the width Wb of the optical waveguide on which each of the time delay parts 40a ₁ ′, 40a ₂ ′, 40a ₃ ′, ..., 40a _{N −1} ′ is formed is equal to the width of the conventional optical waveguide Wa. As a result, the mode in which the optical signal guides may be different, and accordingly, a mode adapter (40b ₁ ', 40b ₁ '', 40b ₂ ', 40b ₂ '', 40b ₃ ', 40b ₃ '' ... 40b _{N -1} ', 40b _{N -1} ') are further included.

Although the preferred embodiments of the present invention have been described above by way of example, the scope of the present invention is not limited to such specific embodiments, and those skilled in the art are appropriate within the scope described in the claims of the present invention. It will be possible to change.

As described above, the present invention having the configuration as described above increases the width of the optical waveguide for changing the propagation constant by using the optical speed changed according to the propagation constant in the optical CDMA, thereby transmitting and receiving data of the transmitter and the receiver. A digital time delay proportional to the time delay of a single optical waveguide can be delayed by increasing the speed and time of the incident optical signal of the encoder and decoder to encrypt and decode, and by increasing the number of time delay portions that increased the width of the optical waveguide. In addition, since the components required for the time delay of the encoder and the decoder system can be eliminated, it is possible to reduce the size and integration of the encoder and the decoder.

Claims (4)

An optical CDMA encoder for delaying and forming and encrypting transmission data converted into an optical signal in an optical waveguide according to a predetermined time code and a wavelength code; An optical CDMA decoder configured to correspond to the encoder to decrypt the encrypted optical signal; At least one time delay unit formed in the optical waveguide having a first width Wa to delay a speed and a time of an optical signal, and having a second width Wb larger than the first width Wa; A mode adapter for optical coupling of heterogeneous waveguides to a boundary between the time delay unit and the optical waveguide; Optical CDMA encoder and decoder using a propagation constant comprising a. The method of claim 1, The speed and time delay of the optical signal is proportional to the magnitude of the second width. The method of claim 1, Speed and time delay of the optical signal is proportional to the length of the time delay portion optical CDMA encoder and decoder using a propagation constant. The method of claim 1, The speed and time delay of the optical signal is proportional to the number of the time delay portion, optical CDMA encoder and decoder using a propagation constant.

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