KR102284163B1 - Multiplexer and Demultiplexer For Dense Wavelength Division Multiplex - Google Patents

Abstract

A technical configuration is proposed to implement a wavelength division multiplexing device with a more dense frequency interval between channels to a level less than 1/2 of the standard frequency interval by using an optical filter technology with a standard frequency interval. A wavelength division multiplexing apparatus according to the present invention comprises: a plurality of first optical filters having a predetermined frequency interval; and a plurality of second optical filters having the same predetermined frequency interval as that of the plurality of first optical filters, and having a passband offset by 1/2 of the predetermined frequency interval compared to the passband of the first optical filter optical filter; and an input part of the second optical filter corresponding to the passband frequency of the first optical filter is connected to the pass part of the first optical filter, and the optical signal primary separated from the first optical filter is received. The second optical filter is configured to separate again into optical signals of the pass section and the reflection section.

Description

Optical multiplexer and demultiplexer for Dense Wavelength Division Multiplex (DeMUX)

The present invention relates to a dense wavelength division multiplexing device, that is, an optical multiplexer and optical demultiplexer (DeMUX) for dense wavelength division multiplexing.

Due to the rapid increase in traffic, the transmission speed of the physical layer is increasing exponentially. WDM (Wavelength Division Multiplexing) technology suitable for broadband transmission networks has already reached saturation, and DWDM (Dense Wavelength Division Multiplexing, Dense Wavelength Division Multiplexing) has been commercialized in response. The backbone network is responding to the rapidly increasing traffic by utilizing such WDM and DWDM.

Mobile communication speed is also developing from 4G to 5G due to the rapid increase in smartphone and wireless data usage. Since it is not possible to cover all the traffic of such high-speed mobile communication with wireless signals, a wired network (optical communication) is mainly used from the base station to the repeater. O-Band that can use direct modulation optical transmission device rather than C and L-band, where expensive transmission device is used for external modulation, for transmission over a distance ranging from several km to 20km in front haul with high-speed transmission of 10Gbps or more is in the spotlight. In the case of O-Band, the transmission loss per km of optical fiber is larger than that of C and L-Band, but since it has the advantage of small dispersion loss, it is advantageous for transmission over a relatively short distance of several to several tens of km.

However, in the case of DWDM according to the recommendations of ITU-T, the frequency interval per channel is 100 GHz or 50 GHz. In the case of C-Band (1525~1565nm) DWDM, which is the most used, if the frequency interval is 100GHz, the wavelength interval is 0.8nm, and if the frequency interval is 50GHz, the wavelength interval is 0.4nm. However, if this standard is equally applied to O-Band (1270~1370nm), the wavelength interval is approximately 0.537nm at 100GHz interval, and when the frequency interval is 50GHz interval, the wavelength interval becomes very narrow to 0.268nm. there is.

Dense Wavelength Division Multiplexing (DWDM) is a technology used to transmit multiple wavelengths on one optical fiber, and a device that collects or separates these different wavelength signals into one optical fiber is required. A device that collects optical signals of different wavelengths is called MUX, and a device that separates them is called DeMux. MUX and DEMUX may be configured using an arrayed waveguide grating (AWG) or a plurality of thin film filters (TFF). However, in the case of AWG, it is difficult to separate signals because the wavelength interval per channel of O-BAND is narrow, and it is difficult to suppress signal interference between adjacent channels. In addition, it is difficult to make a thin film filter with a channel wavelength interval of 0.4 nm even if MUX using general TFF is applied to DWDM of C and L-Band. Moreover, in the case of O-Band, the wavelength interval is 0.268 nm, which is difficult to implement with TFF technology known so far.

In order to implement an O-Band DWDM network, a wavelength division multiplexing technology capable of composing commercially available MUX and DeMUX devices for O-BAND DWDM is essential. In order to realize more dense wavelength division multiplexing even in optical communication bands such as C and L-Band, it is necessary to overcome the limitations of thin film filter manufacturing technology.

An object of the present invention is to provide a wavelength division multiplexing device having optical multiplexing (MUX) and optical demultiplexing (DeMUX) functions for collecting or separating optical signals with very dense wavelength intervals without excessive optical loss. More specifically, an object of the present invention is to provide a configuration of a wavelength division multiplexing device in which the frequency interval between channels is denser to the level of 1/2 or less of the standard frequency interval using an optical filter technology with a standard frequency interval. there is.

In order to solve the above problems, a wavelength division multiplexing apparatus according to the present invention includes a plurality of first optical filters having a predetermined frequency interval; and a plurality of second optical filters having the same predetermined frequency interval as the plurality of first optical filters, and having a passband offset by 1/2 of the predetermined frequency interval compared to the passband of the first optical filter optical filter; wherein the second optical filter corresponding to the passband frequency of the first optical filter has its input part connected to the pass part of the first optical filter, and receives the optical signal primary separated from the first optical filter. The second optical filter is configured to separate again into optical signals of the pass section and the reflection section.

The plurality of first optical filters and the plurality of second optical filters respectively correspond to the plurality of channels having passbands distributed at the predetermined frequency intervals, and the first optical filter of the nth channel and the first optical filter of the nth channel The two optical filters may be connected to each other to form an n-th optical filter group, and the n-th optical filter group may be configured to output optical signals of two sub-channels, respectively.

The first optical filter may be a standard optical filter according to a standard of a communication standard channel grid.

The first optical filter and the second optical filter may be a thin film filter (TFF).

Meanwhile, the wavelength division multiplexing device is configured to offset by 1/2 of the predetermined frequency interval in a direction opposite to the direction in which passband frequencies of the plurality of second optical filters are offset with respect to the plurality of first optical filters. ) of a plurality of third optical filters, wherein the input part of the third optical filter is connected to the reflection part of the second optical filter, and the passband component of the second optical filter is removed from the input optical signal. It may be configured to output an optical signal.

In the wavelength division multiplexing apparatus, the nth optical filter group further includes a third optical filter having the same pass band as the second optical filter of an n-1 channel (where n is a natural number), and the nth optical filter In the third optical filter of the group, the input part is connected to the reflection part of the second optical filter of the n-th channel, and the passband component of the second optical filter of the n-th channel is removed from the input optical signal. may be configured to output

In this case, the plurality of first optical filters are standard optical filters according to a communication standard channel grid standard, the predetermined frequency interval is 100 GHz, and the light output from each passing part of the second optical filter and the third optical filter. The frequency interval of the signal may be configured as 50 GHz.

According to the present invention, there is provided a wavelength division multiplexing device having optical multiplexing and optical demultiplexing functions for collecting or separating optical signals with very dense wavelength intervals without excessive optical loss. More specifically, according to the present invention, it is possible to configure a wavelength division multiplexing device with a more dense frequency interval between channels to a level of 1/2 or less of the standard frequency interval by using an optical filter technology with a standard frequency interval. The present invention has an effect of realizing a wavelength division multiplexing device with an interval of 50 GHz between channels by using, for example, an optical filter technology with an interval of 100 GHz between channels. Using the same optical filter technology, it is also possible to implement a more dense wavelength division multiplexing device with a 25 GHz interval.

1 illustrates a basic configuration and function of a wavelength division multiplexing apparatus using an optical filter.
2 illustrates a basic connection form and function of an optical filter.
3 illustrates a connection form and function of an optical filter group in which a standard frequency interval optical filter and a 1/2 offset (correction) optical filter are connected.
4 illustrates a schematic configuration and function of a wavelength division multiplexing apparatus using the optical filter group of FIG. 3 .
5 illustrates a connection form and function of an optical filter group in which an n-channel standard frequency interval optical filter, a 1/2 offset optical filter, and an n-1 channel 1/2 offset optical filter are connected.
6 illustrates a schematic configuration and function of a wavelength division multiplexing apparatus using the optical filter group of FIG. 5 .

Hereinafter, various embodiments of the present invention will be described with reference to the drawings. The technical spirit of the present invention may be more clearly understood through the embodiments. The present invention is not limited to the embodiments described below.

1 illustrates a basic configuration and function of a wavelength division multiplexing apparatus using an optical filter.

In the wavelength division multiplexing apparatus for performing optical multiplexing and optical demultiplexing functions, the conventional configuration using optical filters includes optical filters 10 as many as the number of channels (N). This figure shows portions of the optical filters 11, 12, and 13 corresponding to three channels that are a part of the N channels. The optical filters 11, 12, and 13 are bandpass filters having a passband in a specific wavelength range around _{each channel center wavelength (λ 1} , λ ₂ , λ _{3 ), and through deposition of an optical thin film} It is composed including the manufactured thin film filter. A plurality of optical filters 11, 12, and 13 are disposed to correspond to the plurality of channels, respectively.

Assuming three channels adjacent to each other, the common part, that is, the incident part, of one optical filter 12 is connected to the reflective part of one adjacent channel optical filter 11, and the passing part outputs the optical signal of the corresponding channel, and reflects The portion is connected to the common portion of the other adjacent channel optical filter 13 . _{In the wavelength division multiplexing device configured in the conventional manner as described above, the wavelength interval between the passband center wavelengths (λ 1} , λ _{2 ,} λ ₃ ) of each of the optical filters 11, 12, 13 of the adjacent channels is the wavelength interval between channels. , and this determines the frequency spacing between channels. In the wavelength division multiplexing apparatus of this type, the interval between the passband center frequencies of each optical filter becomes the frequency interval between channels.

2 illustrates a basic connection form and function of an optical filter.

The optical filter 10 includes a common part to which an optical signal is incident, a pass part to output an optical signal of a pass band, and a reflection part from which an optical signal other than the optical signal of the pass band is output from the incident optical signal. When the wavelength distribution of the optical signal in the reflection part is compared with the wavelength distribution of the optical signal in the common part, attenuation occurs in the wavelength range corresponding to the passband.

3 illustrates a connection form and function of an optical filter group in which a standard frequency interval optical filter and a 1/2 offset optical filter are connected. 4 illustrates a schematic configuration and function of a wavelength division multiplexing apparatus using the optical filter group of FIG. 3 .

A wavelength division multiplexing apparatus according to the present invention includes a plurality of first optical filters having a predetermined frequency interval, and the plurality of first optical filters having the same predetermined frequency interval as the plurality of first optical filters, and a pass band passes through the first optical filter. and a plurality of second optical filters offset by 1/2 of the predetermined frequency interval compared to the band. The input part of the second optical filter corresponding to the passband frequency of the first optical filter is connected to the pass part of the first optical filter, and the optical signal first separated from the first optical filter is transmitted to the second optical filter. is configured to be separated again into optical signals of the passing part and the reflecting part, respectively.

The wavelength division multiplexing apparatus according to an embodiment of the present invention includes a standard frequency interval optical filter 10 (hereinafter abbreviated as a standard optical filter) for each channel for a plurality of channels, and a passband wavelength of the standard optical filter ( 10), the 1/2 offset optical filter 20 offset to the right or left by 1/2 of the standard frequency interval is configured including an optical filter group connected thereto. Here, in the standard optical filter 10 and the 1/2 offset optical filter 20, the optical signal output through the passage of the standard optical filter 10 is inputted back to the 1/2 offset optical filter 20, and the They are connected to each other in a structure such that the two sub-channel optical signals are output separately through the passing unit and the reflecting unit.

Here, the standard optical filter 10 corresponds to the first optical filter, for example, any one of a plurality of optical filters manufactured so that the passband center frequency interval is 100 GHz, the standard optical filter 10 of the nth channel. can be As shown, when the central wavelength of the passband of the n-th channel standard optical filter 10 is λ _n , the 1/2 offset constituting the optical filter group together with the n-th channel standard optical filter 10 the optical filter 20 will have a λ _n 'value is the center wavelength of the pass band of 50GHz offset to the right in the λ _n. As a result, the optical signal passing through the n-th channel standard optical filter 10 passes through the 1/2 offset optical filter 20 again and passes through two sub-channel optical signals, that is, the 1/2 offset optical filter 20 . An optical signal having a wavelength belonging to the band and an optical signal having a wavelength not belonging to the pass band are separated. The 1/2 offset optical filter 20 corresponds to the above-described second optical filter.

In the present specification, the term 'sub-channel' substantially corresponds to each channel of the wavelength division multiplexing device according to the present invention, and is associated with the existing 'channel' corresponding to each of the standard optical filters 10 of the above-described standard frequency interval. used for differentiation.

The wavelength division multiplexing apparatus according to this embodiment includes the optical filter group of FIG. 3 by 1/2 of the total number of channels. For example, six channels may be composed of three optical filter groups including one standard optical filter 10 and one 1/2 offset optical filter 20 . This figure may be understood as illustrating a part of a plurality of channels constituting a wavelength division multiplexing apparatus.

In order to help the understanding of the present invention, a more specific example will be described. The channel grid of ITU-T G.694.1 (C-Band, 100GHz Spacing), which is the most widely used as a DWDM communication standard according to the recommendations of the ITU-T (International Telecommunication Union Telecommunication Standardization Sector), consists of 72 channels as shown below. is done

Channel grid of ITU-T G.694.1 (C-Band, 100GHz Spacing) Dense Wavelength Division Multiplexing (DWDM) ITU Grid: C-Band, 100 GHz Spacing Channel Wavelength Frequency Channel Wavelength Frequency number (nm) (GHz) number (nm) (GHz) One 1577.03 190100 37 1547.72 193700 2 1576.20 190200 38 1546.92 193800 3 1575.37 190300 39 1546.12 193900 4 1574.54 190400 40 1545.32 194000 5 1573.71 190500 41 1544.53 194100 6 1572.89 190600 42 1543.73 194200 7 1572.06 190700 43 1542.94 194300 8 1571.24 190800 44 1542.14 194400 9 1570.42 190900 45 1541.35 194500 10 1569.59 191000 46 1540.56 194600 11 1568.11 191100 47 1539.77 194700 12 1567.95 191200 48 1538.98 194800 13 1567.13 191300 49 1538.19 194900 14 1566.31 191400 50 1537.40 195000 15 1565.50 191500 51 1536.61 195100 16 1564.68 191600 52 1535.82 195200 17 1563.86 191700 53 1535.04 195300 18 1563.05 191800 54 1534.25 195400 19 1562.23 191900 55 1533.47 195500 20 1561.42 192000 56 1532.68 195600 21 1560.61 192100 57 1531.90 195700 22 1559.79 192200 58 1531.12 195800 23 1558.98 192300 59 1530.33 195900 24 1558.17 192400 60 1529.55 196000 25 1557.36 192500 61 1528.77 196100 26 1556.56 192600 62 1527.99 196200 27 1555.75 192700 63 1527.22 196300 28 1554.94 192800 64 1526.44 196400 29 1554.13 192900 65 1525.66 196500 30 1553.33 193000 66 1524.89 196600 31 1552.52 193100 67 1524.11 196700 32 1551.72 193200 68 1523.34 196800 33 1550.92 193300 69 1522.56 196900 34 1550.12 193400 70 1521.79 197000 35 1549.32 193500 71 1521.02 197100 36 1548.52 193600 72 1520.25 197200

Here, 72 optical filter groups are formed by connecting a plurality of standard optical filters corresponding to 72 channels and a plurality of 1/2 offset optical filters having the passband frequency offset by 50 GHz with respect to these standard optical filters, respectively, Through the configuration as partially illustrated in FIG. 4, a wavelength division multiplexing device having 144 sub-channels at intervals of 50 GHz in the same C-Band can be implemented.

Since the plurality of standard optical filters 10 and the plurality of 1/2 offset optical filters 20 have the same frequency interval between channels as 100 GHz, they can be manufactured with the same level of thin film filter manufacturing technology. In conclusion, the wavelength division multiplexing device according to the present invention can provide a wavelength division multiplexing device with a frequency interval that is twice or more dense compared to the level of optical filter manufacturing technology due to the configuration including the optical filter group of the above-described connection structure. will become

Although the example of the C-Band channel grid has been described here, the configuration of the wavelength division multiplexing apparatus according to the present invention is not limited thereto, and may be applied to other wavelength regions such as O-Band. When applied to O-Band (1270~1370nm), if the frequency interval is 100GHz, the wavelength is approximately 0.537nm. It is possible to manufacture an optical filter and a plurality of 1/2 offset optical filters, and by configuring a plurality of optical filter groups connected to each other, a wavelength division multiplexing device having a frequency interval of 50 GHz or more dense than that can be provided. . On the other hand, from another point of view, a wavelength division multiplexing apparatus with an interval of 100 GHz may be implemented using an optical filter technology of the level applied to a conventional wavelength division multiplexing apparatus having a frequency interval of 200 GHz between channels.

5 illustrates a connection form and function of an optical filter group in which an n-channel standard frequency interval optical filter, a 1/2 offset optical filter, and an n-1 channel 1/2 offset optical filter are connected. 6 illustrates a schematic configuration and function of a wavelength division multiplexing apparatus using the optical filter group of FIG. 5 .

Prior to the description of this embodiment, looking at the optical signals of the two sub-channels output from the pass section and the reflector of the 1/2 offset optical filter in FIG. 3, the optical signal on the side of the reflector includes the 1/2 offset light It can be seen that there is a signal component in the passband of the filter. As a result, the degree of isolation between channels is lowered, and there is a possibility that a communication failure may occur due to crosstalk.

The embodiment shown in FIG. 5 presents an optical filter group configured to improve the degree of isolation between channels compared to the embodiments of FIGS. 3 and 4 described above. The optical filter group according to this embodiment includes a standard optical filter 10 of an nth channel among a plurality of standard optical filters having a standard frequency interval, and a passband frequency offset by 1/2 of the standard frequency interval. The n-th channel 1/2 offset optical filter 20 and the n-1 channel 1/2 offset optical filter 30 are included. The half-offset optical filter 20 of the n-th channel and the half-offset optical filter 30 of the n-1 channel do not have pass bands overlapping each other, and the standard frequency interval between the center frequencies of the pass bands. this is formed The 1/2 offset optical filter 30 of the n-1 channel corresponds to the third optical filter, and together with the first optical filter and the second optical filter, constitutes one optical filter group.

Looking at the connection relationship of the optical filter groups according to this embodiment, the common part (input part) of the 1/2 offset optical filter 20 of the n-th channel is connected to the passing part of the n-th channel standard optical filter 10 . and a common part (input part) of the n-1 channel 1/2 offset optical filter 30 is connected to the reflection part of the n-th channel 1/2 offset optical filter 20 . Optical signals of each of the two sub-channels are output from the passing part of the n-th channel 1/2 offset optical filter 20 and the passing part of the n-1 channel 1/2 offset optical filter 30 .

In this way, the signal output from the reflection unit of the 1/2 offset optical filter 20 of the n-th channel by using the 1/2 offset optical filter 30 of the n-1 channel overlaps the passband. By removing the signal component of the wavelength, the degree of separation of signals between sub-channels can be improved. As a result, it is possible to reduce the possibility of failure due to crosstalk.

In the embodiment of Fig. 6, the plurality of standard frequency interval optical filters, that is, the plurality of standard optical filters 11, 12, 13, have a standard frequency interval between channels, for example 100 GHz, and the center frequency of the passband is a communication standard. It may be a plurality of optical filters corresponding to each channel frequency according to . The n-th channel 1/2 offset optical filters 21, 22, and 23 and the n-1 1/2 offset optical filters 31, 32 and 33 are the standard optical filters in terms of frequency spacing between adjacent optical filter groups. It has a frequency interval of 100 GHz as in (11, 12, 13), but offset by 50 GHz (1/2 of the frequency interval) from the pass band of the standard optical filter 11, 12, 13 in terms of the center frequency of the pass band. It may be an optical filter having the characteristics.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto.

Although not shown, it is also possible to implement a wavelength division multiplexing device with an interval of 25 GHz by using a standard optical filter with an interval of 100 GHz by extending the technical idea of the present invention described above. For example, in the above-described embodiment of FIG. 5 , the channel is centered on the pass band of the 1/2 offset optical filter 20 on the pass side of the 1/2 offset optical filter 20 corresponding to the second optical filter. Connecting a fourth optical filter whose pass band is offset by 3/4 of the inter-channel frequency interval with respect to the standard optical filter 10 corresponding to the first optical filter, which is offset by 1/2 of the inter-frequency interval, This is because the fourth optical filter can be extended by adding a fifth optical filter having a passband spaced apart by the frequency interval between the fourth optical filter and the channel by the reflective portion.

10, 11, 12, 13: standard frequency interval optical filter
20, 21, 22, 23: nth channel 1/2 offset optical filter
30, 31, 32, 33: n-1 channel 1/2 offset optical filter

Claims (7)

a plurality of first optical filters having a predetermined frequency interval; and,
The plurality of first optical filters have the same predetermined frequency interval, and their input units are respectively connected to the pass parts of each of the plurality of first optical filters, and the pass band is lower than the pass band of the first optical filters. a plurality of second optical filters offset by 1/2 of the predetermined frequency interval; including,
Each of the plurality of second optical filters transmits the optical signal of each channel that is firstly separated through the passing parts of the plurality of first optical filters, the first sub-channel optical signal outputted through the passing part of the second optical filter, and the second optical signal. The second sub-channel optical signal output through the reflection unit of the optical filter is separated and output again,
The optical signal frequency interval of the plurality of sub-channels composed of the first and second sub-channels respectively corresponding to each of the plurality of second optical filters is configured to be 1/2 of the predetermined frequency interval,
Wavelength division multiplexing device. According to claim 1,
The plurality of first optical filters and the plurality of second optical filters respectively correspond to a plurality of channels having passbands distributed at the predetermined frequency intervals,
The first optical filter of the n-th channel and the second optical filter of the n-th channel are connected to each other to form an n-th optical filter group, wherein the n-th optical filter group is configured to output optical signals of two sub-channels, respectively;
Wavelength division multiplexing device. 3. The method of claim 1 or 2,
The first optical filter is a standard optical filter according to a standard of a communication standard channel grid,
Wavelength division multiplexing device. 3. The method of claim 1 or 2,
The first optical filter and the second optical filter are thin film filters (TFF),
Wavelength division multiplexing device. According to claim 1,
A plurality of third optical filters offset by 1/2 of the predetermined frequency interval in a direction opposite to the direction in which the passband frequencies of the plurality of second optical filters are offset with respect to the plurality of first optical filters including more,
the input part of the third optical filter is connected to the reflection part of the second optical filter to output an optical signal from which the passband component of the second optical filter is removed from the input optical signal;
Wavelength division multiplexing device. 3. The method of claim 2,
The nth optical filter group further includes a third optical filter having the same pass band as the second optical filter of the n-1th channel (where n is a natural number),
The input part of the third optical filter of the nth optical filter group is connected to the reflection part of the second optical filter of the nth channel, and a passband component of the second optical filter of the nth channel among the input optical signals outputting the removed optical signal,
Wavelength division multiplexing device. 7. The method of claim 6,
The plurality of first optical filters are standard optical filters according to a communication standard channel grid standard, the predetermined frequency interval is 100 GHz, and the optical signal output from each passing section of the second optical filter and the third optical filter is obtained. The frequency interval is 50 GHz,
Wavelength division multiplexing device.

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