KR20000004569A - Add/drop multiplexer for wavelength division multiplexing transfer - Google Patents

Abstract

PURPOSE: An add/drop multiplexer is provided to reduce occupation area of network by using a reflecting structure in which the inputted wavelength channel is reflected and output. CONSTITUTION: An optical input/output part inputs an optical signal which is inputted from outside, or outputs a transmitted optical signal to outside. A router reflects the optical signal transmitted from the optical input/output part or an optical switching part and outputs the optical signal to the optical input/output part or an optical switching part by using a first reflection mirror(511). The optical switching part reflects the optical signal transmitted from the router and transmits to the router, or performs a switching process about the dropped optical signal so that the adding process is to be achieved by using a second reflection mirror(517). Accordingly, a 2x2 optical switch structure and an arrayed wave guide grating router(AWGR) structure can be reduced in a half volume by using the first reflection mirror and second reflection mirror, respectively.

Description

Add / drop multiplexer for wavelength division multiplexed transmission

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an add / drop multiplexer for wavelength division multiplexing transmission. In particular, the present invention relates to selectively loading data on a desired wavelength channel at each node of a network using wavelength division multiplexing. An add / drop multiplexer for dropping, adding, and simple passing.

The wavelength division multiplexed transmission method has been proposed as one of the methods to increase the transmission capacity by using the optical fiber that has been installed. Such a wavelength division multiplexing transmission method transmits optical signal information using a channel having multiple wavelengths in one optical fiber based on the large transmission capacity of the optical fiber. Based on the wavelength division multiplexing transmission scheme, a network connecting nodes transmits data carried on a channel having a desired wavelength using an add / drop multiplexer.

However, the conventional add / drop multiplexer is designed such that the output side of the same structure as the input side structure into which the wavelength channel is input is symmetrical, so that the occupied area of the device is too large, which makes it difficult to integrate the device.

Accordingly, the present invention has been made to solve the above problems, in forming a network connecting nodes using a wavelength division multiplexing transmission method, the reflection to reflect and output the input wavelength channel The purpose of this structure is to provide an add / drop multiplexer that not only significantly reduces the design area but also implements wavelength channel monitoring.

1 is a conceptual explanatory diagram of an add / drop multiplexer for a general wavelength division multiplexed transmission;

Figure 2 is a configuration diagram of one embodiment of an arrayed waveguide grating router (AWGR) applied to the present invention.

Figure 3 is a configuration diagram of one embodiment of a 2x2 optical switch applied to the present invention.

Figure 4 is an exemplary configuration for explaining the structural symmetry of the addition / drop multiplexer of the present invention.

5 is a block diagram of an embodiment of an add / drop multiplexer for wavelength division multiplexed transmission using a reflector according to the present invention.

Explanation of symbols on the main parts of the drawings

511: first reflecting mirror 512: phase shifter

513: 3 dB coupler 514, 520: optical waveguide

515: slab waveguide 516: lattice arm

517: Second reflector 518, 519: Input and output optical waveguide

521: antireflection film

In order to achieve the above object, the present invention provides an addition / drop multiplexer for wavelength division multiplexing transmission, comprising: light input / output means for inputting an optical signal input from the outside or outputting the transmitted optical signal to the outside; Routing means for distributing an optical signal transmitted from the light input / output means or the light switching means and transmitting the light signal to the light input / output means or the light switching means, and simplifying the structure without reducing the transmission path by using a first half mirror; And reflecting the optical signal transmitted from the routing means and applying it to the routing means, or switching to add to the dropped optical signal, and simplifying the structure without reducing the transmission path by using the second reflector. Optical switching means.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1 is a conceptual explanatory diagram of a general add / drop multiplexer for wavelength division multiplexing transmission, and receives a plurality of wavelength channels through an input port IP11 and through an output port OP11. It outputs a plurality of wavelength channels, receives a wavelength channel to be used for addition through a plurality of addition channel input ports AP2 to APn, and outputs a dropped wavelength channel through a plurality of drop channel output ports DP2 to DPn. .

As shown in FIG. 1, channels of different wavelengths λ1 to λn enter the input port IP11 of the add / drop multiplexer 110 at a point in the network, of which the final The two wavelengths are dropped at that point, and one of the two free wavelength channels thus created carries the new data sent from that point to another point, and the channel passing through the other point passes through the output port. The function to output through (OP11) is illustrated. The wavelength channel of the data received at each point is variable, and the data to be sent is variable because the data to be sent must be carried in the empty wavelength channel. Therefore, the add / drop multiplexer 110 must have reconfugruability to drop or add any wavelength.

FIG. 2 is a diagram illustrating an embodiment of an arrayed waveguide grating router (AWGR) applied to the present invention and shows 8 × 8 AWGR.

As shown in FIG. 2, the 8x8 AWGR includes a plurality of reverse memory input waveguides 210 having a first side end connected to a plurality of input ports IP21 to IP28, and a plurality of inverted first side ends. An input slab optical waveguide 220 connected to the second side end of the meso-type input optical waveguide 210, and a plurality of digital couplings connected to the second side end of the input slab optical waveguide 220. A grating arm 230 and a first side end are provided with a plurality of dishing arms. The output slab optical waveguide 240 connected to the second side end of the grating arm 230, the first side end is connected to the second side end of the output slab optical waveguide 240, and the second side end has a plurality of Multiple needles connected to the output ports OP21 to OP28 of A) output waveguide 250 is provided.

Referring to the 8x8 AWGR applied to the present invention having the structure as described above in detail.

When a signal is input to multiple wavelength channels through each of the input ports IP1 to IP8, the signals are sent to the respective output ports OP1 to OP8 according to the wavelength. In 8x8 AWGR, only one wavelength can be connected to a specific input and output port. Therefore, when a signal is simultaneously sent from multiple input ports to the same one output port, since the required wavelength is different for each input port, there is no collision between signals at the output port. In addition, due to the cyclical use of wavelengths, nxn connections are generally possible at n different wavelengths. As described above, the function of the 8x8 AWGR described above is based on interference phenomena, which are physical properties of light, which are described in reference (H. Takahashi, K. Oda, H. Toba, and Y. Inoue, "Transmission characteristics"). of arrayed waveguide NxN waveleng multiplexer ", Journal of Lightwave Technology vol. 13, no. 3, March 1995.).

In particular, in the structure of the 8x8 AWGR shown in FIG. 2, it is noted that due to the symmetry of the structure, the size of the AWGR can be reduced by half by using a structure using a reflector and sharing an input / output port. If the reflector is installed at the position of the symmetry line shown in FIG. 2 and the input optical waveguide 210 and the output optical waveguide 250 are shared, AWGR can be realized in half the size. A description of this is described in detail in H. Okayama, M. Kawahra, and T. Kamijoh, "Reflective waveguide array demultiplexer in LiNbO ₃ ", Journal of Lightwave Technology vol. 14, no. 6, June 1996. have.

3 is a schematic diagram of an embodiment of a 2x2 optical switch according to the present invention, which is a 2x2 optical switch using a Mach Zehnder interferometer structure.

As shown in FIG. 3, the 2x2 optical switch has an input optical waveguide 311 and 312 connected to the input ports IP31 and IP2, and an output optical waveguide 313 connected to the output ports OP31 and OP32, respectively. 314, between the 3dB coupler 315 connected to the input optical waveguides 311 and 312, between the 3dB coupler 316 connected to the output optical waveguides 313 and 314, and between the 3dB coupler 315 and 316. A phase shifter 317 that is connected in a curve and transmits an optical signal transmitted through the input optical waveguide 311 to the output optical waveguide 313 and is connected in a straight line between the 3dB couplers 315 and 316 to input the optical signal. And a phase shifter 318 for transmitting the optical signal transmitted through the waveguide 312 to the output optical waveguide 314.

A detailed description of the conventional Mach gender interferer having the structure as described above is as follows.

The optical signal transmitted through the input optical waveguides 311 and 312 is branched by 50% through the 3dB coupler 315 and transmitted to the phase shifters 317 and 318. In this way, the optical signal branched through the 3dB coupler 315 passes through the phase shifters 317 and 318 and then recombines at the 3dB coupler 316 at the rear end. At this time, if the phase difference generated between the phase shifters 317 and 318 is an odd multiple of 180 °, it is output to the output port opposite to the input optical waveguide. If the phase difference is even multiple of 180 °, the output of the input optical waveguide direction is output. Output to the port. That is, according to the phase difference in the phase shifters 317 and 318, it is determined to which output optical waveguide the branched optical signal is coupled out.

Accordingly, as shown in the conceptual diagram of the switch function of FIG. 3, the 2 × 2 optical switch 300 may include a bar-state 319 in which input ports IP31 and IP32 and output ports OP31 and OP32 are connected side by side. The cross-state 320b may be selectively adjusted by electrical manipulation of the phase shifters 317 and 318. The phase shifters 317 and 318 may be implemented by using an electro-optic effect of changing a refractive index of a material by applying a voltage, and the 3dB couplers 315 and 316 may be implemented using a directional coupler. A detailed description of these physical theories is well presented in Theodor Tamir, "Guided-wave optpelectronics" 2nd edition published by Springer-Verlag, pp. 174-181, 1990. Note that in the structure of the 2x2 optical switch 300, due to the symmetry of the switch structure, as in the case of the AWGR of Figure 2, it can be implemented in a half size by applying a structure using a reflector.

FIG. 4 is an exemplary configuration diagram of the addition / drop multiplexer of the present invention configured by combining the AWGR of FIG. 2 and the 2x2 optical switch of FIG. 3, and includes a plurality of addition channel input ports and a dropping wavelength channel for receiving a wavelength channel for addition. Nxn AWGR 410 and input / output ports which are connected to a plurality of dropping channel output ports which are output, and connected to an input port IP41 and an output port OP41, respectively, and an input channel input port of the nxn AWGR 410, respectively. A plurality of 2x2 optical switches 422 to 42n connected to the drop channel output ports and connected to the drop channel output ports DP2 to DPn and the add channel input ports AP2 to APn.

The addition / dropping multiplexer having the structure as described above will be described in detail as follows.

The input terminal of the nxn AWGR 410 connected to the input port IP41 is used as an input terminal of the add / drop multiplexer 400, and the output terminal of the nxn AWGR 410 connected to the output port OP41 is added / drop multiplexer 400. Used as the output terminal of.

Channels of various wavelengths input through the input / drop multiplexer 400 are divided into wavelengths and then transmitted to the plurality of 2x2 optical switches 422 to 42n through respective output terminals of the nxn AWGR 410. The channels of the given wavelengths determine whether the signal is dropped or passed depending on the state of each of the 2x2 optical switches 422 to 42n.

For example, λ _i of the wavelength channels input through the input terminal of the nxn AWGR 410 connected to the input port IP41 goes out to the i-th output terminal of the nxn AWGR 410 to open the i-th 2x2 optical switch 42i. Will pass. At this time, if the i-th 2x2 optical switch 42i is cross-state, the input wavelength channel λ _i is dropped, and if the 2x2 optical switch 42i is side-by-side connected, nxn As it enters the i-th input of the AWGR 410, and as a result is output through the output of the nxn AWGR 410 connected to the output port OP41, λ _i passes through the add / drop multiplexer 400. . That is, when the desired wavelength drops, the wavelength channel becomes empty, so that new data can be added to the channel. And addition and descent can occur simultaneously.

The addition / dropping multiplexer 400 combining the nxn AWGR 410 and the 2x2 optical switches 422 to 42n illustrated in FIG. 4 may use InP or LiNbO ₃ as a substrate having a large electro-optic coefficient. Can be integrated on the same substrate. A detailed description of this can be found in CGM Vreebug, T. Uetterdijk, YS Oei, MK Smith, FH Groen, EG Metaal, P. Demeester, and HJ Frankena, "First InP-based reconfigurable intergrated add-drop multiplexer", IEEE Photonics Technology letters, vol. 9, no. 2, February 1997). In designing and fabricating integrated optical devices, it is very important to minimize the area of the entire device.

As described above, applying the structure using the reflector based on the structural symmetry of the AWGR and the 2x2 optical switch, the area of the addition / drop multiplexer of the present invention is invented using the principle of reducing the size of each device in half. An integrated structure capable of minimizing the number will be described with reference to FIG. 5.

5 is a block diagram of an addition / drop multiplexer for wavelength division multiplexing transmission according to an embodiment of the present invention.

As shown in FIG. 5, the addition / drop multiplexer for wavelength division multiplexing transmission of the present invention includes a plurality of first reflectors 511 for reflecting transmitted optical signals, and a plurality of left ends connected to the first reflectors 511. A plurality of 3dB couplers 513 and a plurality of 3dB couplers 513 that couple a pair of phase shifters 512, a wavelength channel coupled to and transmitted to the right end of the plurality of pairs of phase shifters 511. A plurality of optical waveguides 514 connected to the first side and transmitting the reflected and transmitted wavelength channels, a slab optical waveguide 515 connected to the plurality of optical waveguides 514 with a first side end, and a first side end A plurality of grating arms 516 connected to the second side end of the slab optical waveguide 515 and a wavelength transmitted through the grating arms 516 connected to the second side ends of the plurality of grating arms 516. An input / output connected with a second reflector 517 for reflecting a channel and a first side end connected to a first side end of the plurality of grating arms 516 The waveguides 518 and 519, a plurality of optical waveguides 520 having a first side end connected to a second side of the plurality of 3dB couplers 513, and both ends of the waveguides 518 and 519 to the first and second reflectors 511 and 517. And an anti-reflection film 521 connected to a second side end of the input / output optical waveguides 518 and 519 and a second side end of the plurality of optical waveguides 520 to prevent reflection of the wavelength channel.

In addition, an external device for inputting / outputting a wavelength channel to the addition / dropping multiplexer 500 is connected to the input / output optical waveguides 518 and 519 and the plurality of optical waveguides 520, wherein the external device is shown in FIG. 5. It can be configured as.

The external device may include input / output optical fibers 522 and 523 having a first end connected to optical waveguides 518 and 519, and a plurality of optical fibers connected to a second side end of a plurality of optical waveguides 520. 524 and a plurality of wavelength channels are respectively connected to input ports IP51 and IP52, and output ports OP51 and OP52 are respectively output wavelength channels, respectively. A plurality of circulators 525 and 526 connected to the second side and a plurality of addition channel input ports AP51 to AP56 for inputting a wavelength channel to be added are respectively connected, and a plurality of dropped wavelength channels are output. The falling channel output ports DP51 to DP56 are connected to each other, and are configured of a plurality of circulators 527 to 533 connected to the second side ends of the plurality of optical fibers 524.

The basic operation is as described with reference to FIGS. 1 to 4, and the present invention employs a 2x2 optical switch and an AWGR structure using the first and second reflectors 511 and 517, respectively. It is reducing the total area to half of its existing size and is also expandable. This is compared with the structure of the 2x2 optical switch 300 of the addition / drop multiplexer 500 and the structure of the 2x2 optical switch 300 of FIG. 3, compared to the structure of the 2x2 optical switch 300, the 2x2 optical switch structure of FIG. As shown in FIG. 2, the structure of the AWGR of FIG. 2 is reduced by half compared to the structure of the AWGR of FIG. 2. It can be seen that. However, if there is a difference, the add / drop multiplexer 500 of FIG. 5 receives the wavelength channel through the input / output optical waveguides 518 and 519 and outputs the reflected optical signal.

In particular, in order to reduce the loss of the entire element, the reflectance of the first and second reflectors 511 and 517 is preferably 100%, and is provided at one end of the input / output optical waveguides 518 and 519 and the plurality of optical waveguides 520. The reflectance of the anti-reflection film 524 is preferably set to 0%. If the reflectance of the first reflector 511 has a value smaller than 100%, the loss of the total addition / dropping multiplexer 500 element is slightly increased, but there is always an optical signal passing through the first reflector 511. This enables the implementation of wavelength channel monitoring. This is very important in terms of management of the network, and is an important advantage along with the size reduction of the addition / multiplexer 500 structure of the present invention. However, there was no such function before.

The operation of the addition / drop multiplexer of the present invention having such a structure will be described in detail as follows.

When six wavelength channels λ ₃ to λ ₈ are input through the input port IP51, the six wavelength channels are distributed in the slab optical waveguide 515 and transmitted to the plurality of grating arms 516. After traveling along the optical waveguide of the grating arm 516, it is reflected by the second reflector 517 and returned to the slab optical waveguide 515 to be dispersed again. The wavelength channels are separated and transmitted to a plurality of optical waveguides 514 for each wavelength, and then proceed to a plurality of 3dB couplers 513 and a plurality of phase shifters 512 constituting a 2x2 optical switch.

In this way, each wavelength channel entering the 2x2 optical switch portion is reflected back from the first reflector 511, and then returns to the optical waveguide entered by the electrical manipulation of the plurality of phase shifters 512, or Through the optical waveguide 520 and the plurality of optical fibers 524, it is determined whether to be output to the outside through one of the drop channel output ports of the drop channel output ports DP51 to DP56. At this time, if the wavelength channel is output through the falling channel output port, the wavelength channel is dropped.

If it is returned to the transmitted optical waveguide, the reflected wavelength channel is output through the input port IP51 through the reflection process by the second reflector 517 as described above by the characteristics of the AWGR.

Also, a plurality of circulators 525 to 532 are attached to the input / output optical fibers 522 and 523 and the plurality of optical fibers 524, respectively, so that optical signals returned through the optical fibers are output ports OP51 and OP52. Or it is output through the drop channel output ports DP51 to DP56. Further, when the drop occurs on the principle as described above, the addition is possible by inputting the wavelength channel to be added through the addition channel input ports AP51 to AP56. When a signal is input through each of the addition channel input ports AP51 to AP56, and the corresponding phase shifter is in a cross-connected state, the signal to be added is passed through the coupler 513 and the optical waveguide 514 to the slab waveguide 515. After entering and dispersed and proceeding, the beam proceeds to the grating arm 516 and is reflected by the second reflector 517. In this way, the reflected signal is again passed through the grating arm 516 and the slab waveguide 515, through the input and output waveguides 518 or 519 by the characteristics of the AWGR as described above, and eventually the corresponding output port (OP51 or OP52). This adds up. It should be noted, however, that a wavelength channel for adding to each output port OP51 or OP52 is determined for each of the addition channel input ports AP51 to AP56. For example, if you want the addition to the output port (OP51) by the joining channel input port (AP52), the wavelength channels (λ ₇₎ only sseuyimyeo output port wavelength channels will be to the addition to the (OP52) (λ ₇₎ only Used. This is due to the characteristics of the AWGR.

In the above, the input / output process of the wavelength channel through the input port IP51 and the output port OP51 has been described, but the process of inputting / outputting the wavelength channel through the input port IP52 and the output port OP52 is the same as the above-described process. Do. As such, the reason for having a pair of input / output terminal structures is to implement a bi-directional ring network.

If this is not the case, a structure having only one input / output stage is possible. When the structure proposed in the present invention is used, the number of wavelength channels in each direction should be half of that of the circular structure, and the wavelength channels should be selected so that the signals coming into the input ports IP51 and IP52 do not go through the same phase shifter. do. For example, in the case of FIG. 5, if only one input port is used, a total of six wavelength channels λ ₃ to λ ₈ can be used, and when two input ports are used, three wavelength channels λ ₄ and λ ₆ , respectively , λ ₈ ) becomes available.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

As described above, the addition / drop multiplexer for wavelength division multiplexing transmission according to the present invention reduces the 2 × 2 optical switch structure by half by using the first reflector 511 and reduces the AWGR structure by the second reflector 517. By reducing it by half compared to the conventional, the overall area is reduced by about half, which can increase the integration rate of the device. In addition, there is a very excellent effect of monitoring the wavelength channel by using a signal that is transmitted without being reflected through reflectance adjustment of the first reflector 511.

Claims (8)

In the addition / drop multiplexer for wavelength division multiplexing transmission, Light input / output means for inputting an optical signal input from the outside or outputting the transmitted optical signal to the outside; Routing means for distributing an optical signal transmitted from the light input / output means or the light switching means and transmitting the light signal to the light input / output means or the light switching means, and simplifying the structure without reducing the transmission path by using a first half mirror; And The optical signal transmitted from the routing means is reflected and applied to the routing means, or switched to add to the dropped optical signal, and the light is simplified by using a second reflector without reducing the transmission path. Switching means Addition / drop multiplexer for wavelength division multiplexed transmission comprising a. The method of claim 1, The routing means, The first reflector for reflecting the transmitted optical signal; At least one input / output optical waveguide for receiving an optical signal transmitted from the outside and outputting the optical signal to the outside; And Arrayed Waveguide Grating Router (AWGR) connected between the at least one input / output optical waveguide and the first reflector. Addition / drop multiplexer for wavelength division multiplexed transmission comprising a. The method of claim 2, The AWGR, A slab optical waveguide having a first side end coupled to the at least one input / output optical waveguide for transmitting an optical signal; A plurality of grating arms connected between the second side end of the slab optical waveguide and the first reflector for transmitting an optical signal; And At least one first optical waveguide spaced apart from the at least one input / output optical waveguide and connected to a first side end of the slab optical waveguide for transmitting an optical signal inputted to the slab optical waveguide Addition / drop multiplexer for wavelength division multiplexed transmission comprising a. The method of claim 3, wherein The optical switching means, The second reflector for reflecting the transmitted optical signal; And 2x2 optical switch connected between the second reflector and the AWGR Addition / drop multiplexer for wavelength division multiplexed transmission comprising a. The method of claim 4, wherein The 2x2 optical switch, At least a pair of phase shifters having a first side end connected to the second reflector to shift the phase of the optical signal reflected from the second reflector; At least one coupler, an upper side of the first side end coupled to the at least one first optical waveguide, and a second side end coupled to the at least one pair of phase shifters for coupling the transmitted optical signal; And At least one second optical waveguide connected at one side to a lower side of the first side end of the at least one coupler to transmit an optical signal Addition / drop multiplexer for wavelength division multiplexed transmission comprising a. The method according to claim 2 or 4, Anti-reflection film to prevent reflection of unnecessary optical signals Addition / drop multiplexer for wavelength division multiplexed transmission further comprising. The method of claim 5, Each of the at least one coupler, An addition / dropping multiplexer for wavelength division multiplexing transmission, characterized in that it is a 3 dB coupler. The method of claim 1, The second reflector is adjustable transmittance, the addition / drop multiplexer for wavelength division multiplexed transmission, characterized in that for monitoring the channel using the wavelength channel transmitted through it.