JP2002027511A - High-speed data transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To concurrently transmit a high-speed data calling of an xDSL subscriber and a switching calling of a telephone subscriber in a set of optical cables between an accommodation station and a remote terminal device. SOLUTION: The other empty fixing band than a switching calling 91 of a telephone subscriber 1 is allocated to a data calling 92 of an xDSL subscriber 2 under control of a remote terminal device 3 connected via an accommodation station 4 and an optical cable 8 within the remote terminal device 3. The data calling 92 and switching calling 91 are STM-multiplexed, and can be collected in the accommodation station 4 by a set of optical cables 8. A directional route distributor 41 or switcher 42 of the accommodation station 4 terminates the optical cable 8, and the data calling 92 and switching calling 91 multiplexed by the remote terminal device 3 are separated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to xDSL (xDSL) for performing high-speed data transmission using copper wire used for conventional telephone communication.
The present invention relates to a switching system capable of high-speed data transmission using Digital Subscriber Line (Digital Subscriber Line) technology, and particularly to a subscriber accommodated via a copper wire in a remote terminal connected to an accommodation station via an optical cable. Using xDSL technology,
The present invention relates to a switching system that realizes high-speed data transmission.

[0002]

2. Description of the Related Art In recent years, an xDSL service has been provided which realizes high-speed data transmission by connecting a dedicated modem to a pair of existing copper wires. xDSL technology, from several kHz to several M over copper wire
This is a technology that uses a high frequency band of up to Hz and modulates the subscriber signal with a dedicated modem and transmits it.Compared to conventional telephone communication that communicates by flowing a signal in the frequency band of 4 kHz or less. Much faster (hundreds of kbit / s to tens of Mb
It / s) signal transmission can be performed.
xDSL technology depends on the number of copper wire pairs used, whether there is a difference between upstream and downstream speeds, transmission speed, transmission distance, etc.
There are several types such as L, HDSL, SDSL, SHDSL, SSDSL, VDSL, etc.

FIG. 7 is a block diagram showing the configuration of a switching system according to the prior art which enables high-speed data transmission using an asymmetric digital subscriber line technology (ADSL), which is one of xDSL technologies. Hereinafter, a conventional switching system will be described with reference to FIG. In FIG. 7, 2a is an ADSL subscriber, 21 is a telephone terminal, etc., 22 is a data terminal, etc., 23a is a subscriber side splitter, 24a is a subscriber side ADSL modem, 4 is an accommodation station, 42 is a switching device,
3a is an ADSL multiplexing device, 431a is an office-side splitter, 43
2a is a station side ADSL modem, 433a is a data demultiplexing unit,
5 is a public / private line network, 6 is a data network, and 71 is a copper wire.

ADSL is an asymmetric digital subscriber line technology for realizing a signal transmission speed of several Mbit / s using a frequency band of about 30 kHz to 1 MHz. As shown in FIG. This is realized by connecting the ADSL subscriber 2a via the copper wire 71. The ADSL subscriber 2a has a telephone terminal 21, etc.
It comprises a data terminal 22, a subscriber-side splitter 23a, and a subscriber-side ADSL modem 24a.
Comprises an exchange device 42 and an ADSL multiplexing device 43a. The ADSL multiplexing device 43a includes a station-side splitter 431a for the subscriber, a station-side ADSL modem 432a, and a data multiplexing / demultiplexing unit 433a.

In FIG. 7, a digital signal (hereinafter, referred to as a data call 92a) transmitted from a data terminal or the like 22 of the ADSL subscriber 2a connected to the accommodation station 4 via a copper wire 71 is a subscriber ADSL modem. ADSL that has been D / A converted by 24a and then modulated to a frequency band of about 30kHz to 1MHz
The signal 93a is transmitted to the subscriber side splitter 23a. The subscriber-side splitter 23a multiplexes the ADSL signal 93a and an analog signal (hereinafter, referred to as a switched call 91a) using a frequency band of 4 kHz or less sent from the telephone terminal 21 and transmits the multiplexed signal over the copper wire 71. Transmitted to Containment Station 4
The ADSL signal 93a and the switched call 91a are separated by the office-side splitter 431a having a function of separating the frequency band of the ADSL signal 93a and the frequency band of the switched call 91a. Then, the ADSL signal 93a is returned to the original data call 92a by the station side ADSL modem 432a, and the data demultiplexer 433a
Is transmitted to the data network 6 via
The data is sent to the public / private line network 5 through the existing switching processing in the switching device 42.

The operation on the upstream side (subscriber → accommodation station) has been described above, but the same applies to the operation on the downstream side (accommodation station → subscriber). As mentioned above, the conventional AD
The switching system that enables high-speed data transmission using SL is based on the existing copper wire 71 between the accommodation station 4 and the ADSL subscriber 2a.
, The exchange call 91a and the data call 92a can be transmitted simultaneously, and the high-speed transmission of the data call 92a can be performed.

[0007] As a conventional technique relating to a switching system which enables this kind of high-speed data transmission, for example, a technique described in Japanese Patent Application Laid-Open No. 11-355435 is known.

[0008]

The prior art described above is
No consideration has been given to the case where an optical cable is inserted in a part of the section between the accommodation station and the subscriber, and in response to the conversion of optical signals to wiring points (feed points) and access points, There is a problem in that xDSL services cannot be provided to subscribers located under manholes, on telephone poles, in user buildings, and under a remote terminal device connected to an accommodation station via an optical cable.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide an xDSL service to a subscriber under a remote terminal unit connected via an optical network and an accommodation station. To make it possible, data calls of xDSL subscribers and exchange calls of telephone subscribers can be simultaneously transmitted over a pair of optical cables between the accommodation station and the remote terminal equipment, and high-speed data transmission has been made possible. An exchange system is provided.

[0010]

According to the present invention, there is provided a remote terminal for accommodating a telephone subscriber and an xDSL subscriber, an accommodation station, and an optical cable for connecting the remote terminal and the accommodation station. Wherein the remote terminating device allocates a free fixed band different from the switched call from the telephone subscriber to the data call from the xDSL subscriber, and sets the data call and the switched call to STM. Means for multiplexing, the accommodating station terminates the optical cable, and comprises means for separating the data call and the switched call multiplexed by a remote terminal device. STM which is connected to the data network, public network and private network, and exchanges data calls from xDSL subscribers received from the data network and exchange calls from telephone subscribers received from public and private network.
This is achieved by providing means for multiplexing and transmitting to the remote terminating device via the optical cable.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a switching system capable of high-speed data transmission according to the present invention.

FIG. 1 is a block diagram showing a configuration of a switching system according to an embodiment of the present invention, FIG. 2 is a block diagram showing a configuration example of an existing switched call processing unit, and FIG. 3 is a configuration example of an xDSL subscriber accommodation unit. FIG. 4 is a block diagram showing an example of the configuration of an xDSL multiplexer, and FIG. 5 is a diagram for explaining an example of a multiplexing method for a data call of an xDSL subscriber and a switched call of a telephone subscriber. 1 to 5, 1 is a telephone subscriber, 2 is an xDSL subscriber, 3 is a remote terminator, 11 is an A (analog) subscriber, 12 is an I (ISDN) subscriber, and 13 is an L (dedicated line). The subscriber, 23 is the subscriber side splitter, 24 is the subscriber side xDSL modem, 31 is the existing switched call processing unit, 32 is the xDSL subscriber accommodation unit, 41 is the route distribution device, 43 is the xDSL multiplexing device, and 72 is the xDSL multiplexing device. It is a copper wire / optical fiber, and other reference numerals are the same as those in FIG.

[0013] An exchange system according to an embodiment of the present invention comprises:
A telephone subscriber 1 and an xDSL subscriber 2 are accommodated under a remote terminal device 3 connected to an accommodation station 4 via an optical cable 8. The telephone subscriber 1 may be an A (analog) subscriber 11, an I (ISDN) subscriber 12, an L (dedicated line) subscriber 13, etc., and the xDSL subscriber 2 may be a telephone terminal 2
1, a data terminal 22, a subscriber-side splitter 23, and a subscriber-side xDSL modem 24. The remote terminating device 3 includes an existing switching call processing unit 31 and an xDSL subscriber accommodating unit 32, and the accommodation station 4 includes a route distribution device 41, a switching device 42, and an xDSL multiplexing device 43. ing.

In the embodiment of the present invention configured as described above, data is transmitted / received from the data terminal or the like 22 in the xDSL subscriber 2, and is transmitted from the subscriber side xDSL modem 24 to the remote terminal 3.
Copper wire 7 using xDSL technology with the xDSL subscriber accommodation unit 32
A digital signal (hereinafter, referred to as a data call 92) transmitted at high speed over a telephone 1 and a telephone terminal 2 in the xDSL subscriber 2
1 and A subscriber 11 and I subscriber 1 as telephone subscriber 1
The transmission path for voice or data (hereinafter referred to as a switched call 91) transmitted and received from the L2 and L subscribers 13 is based on the existing switched call processing unit 31 and the xDSL subscriber accommodating unit 32 in the remote terminal 3 and the optical cable 8 And the route distribution device 4 in the accommodation station 4
1 or switching device 42, xDSL multiplexing device 43,
It comprises a dedicated line network 5 and a data network 6.

The xDSL subscriber accommodating section 32 in the remote terminal 3 shown in FIG. 1 processes a switched call 91 and a data call 92 of the xDSL subscriber 2, and is newly installed in the remote terminal 3 according to the present invention. Is what is done. xDSL subscriber accommodation unit 32
Is, as shown in FIG. 3, a station-side splitter 321 and a station-side splitter 321.
It comprises an xDSL modem 322 and an xDSL data demultiplexing unit 323. Then, the office-side splitter 321 is connected to the subscriber-side splitter 2 in the xDSL subscriber 2 via the copper wire 71.
3 and has a function of separating a switching call 91 from the telephone terminal 21 or the like superimposed by the subscriber side splitter 23 and an xDSL signal 93 from the subscriber side xDSL modem 24 by a frequency band. The switching call 91 having the frequency band is connected to the A subscriber IF 311 in the existing switching call processing unit 31, and the xDSL signal 93 having the frequency band of 4 kHz or more is transmitted to the station side xD.
Connect to SL modem 322. Also, the existing switched call processing unit 3
1, the exchange call 91 from the A subscriber IF 311 and the station side xD
The xDSL signal 93 from the SL modem 322 is multiplexed with the
Has a function of connecting to the subscriber-side splitter 23 in the xDSL subscriber 2 via the. Note that the office-side splitter 321 and the subscriber-side splitter 23 may not be installed depending on the xDSL system.

The office-side xDSL modem 322 shown in FIG.
Is the station-side splitter 321 and the xDSL data demultiplexing unit 32
3 and an analog signal xDSL signal 93 having a frequency band of 4 kHz or more to a digital signal data call 92, and a digital signal data call 9
An analog signal with a frequency band of 2 to 4 kHz or more
Convert to xDSL signal 93. Also, the station side xDSL modem 322
Is connected to the subscriber side xDSL modem 24 via the copper wire 71, whereby the remote terminating device 3 and the xDSL subscriber 2
That is, it is possible to simultaneously transmit the switched call 91 and the data call 92 using the existing copper wire 71 between them, and to perform the high-speed transmission of the data call 92. Further, the xDSL subscriber accommodating section 32 is configured by installing a plurality of sets of the office-side splitter 321 and the office-side xDSL modem 322, and thereby can accommodate a plurality of xDSL subscribers 2. ing.

The xDSL data demultiplexing unit 323 shown in FIG.
Multiplexes the data calls 92 received from the plurality of station-side xDSL modems 322, transmits the multiplexed signal to the switching call demultiplexing unit 314 in the existing switching call processing unit 31, and Of the multiplexed data call 92 received from the switching call demultiplexing unit 314 of the
Send to SL modem 322. As a result, xDSL subscriber 2
It is possible to connect the switched call 91 and the data call 92 to the existing switched call processing unit 31 which is the existing unit of the remote terminal device 3.

The existing switched call processing section 31 in the remote terminal 3 shown in FIG. 1 processes the switched call 91 of the telephone subscriber 1, and has a function which the remote terminal 3 has conventionally. As shown in FIG. 2, the existing switched call processing unit 31
F311, I subscriber IF 312, L subscriber IF31
3, the switched call demultiplexer 314, and the optical-electrical converter 31
And 5. A subscriber IF 311 shown in FIG.
Has an interface with the A subscriber 11 connected by the copper wire 71 and performs bidirectional processing such as A / D conversion and D / A conversion of a conventional analog telephone signal using a frequency band of 4 kHz or less, Also, in response to the exchange call 91 of the xDSL subscriber 2 from the office side splitter 321 in the xDSL subscriber accommodation unit 32,
The same bidirectional processing as the A subscriber 11 is performed.

The I-subscriber IF 312 shown in FIG. 2 has an interface with the I-subscriber 12 connected by a copper wire or an optical cable (hereinafter, referred to as a copper wire / optical fiber 72).
IS with a transmission speed of 128 k, 1.5 Mbit / s, etc.
Performs bidirectional processing of DN digital signals. The L-subscriber IF 313 shown in FIG. 2 has an interface with the L-subscriber 13 connected by the copper wire / optical fiber 7, and
k, 128k, 192k, 256k, 384k, 512
k, 768 k, 1M, bidirectional processing of digital leased line signals having a transmission rate of 1.5 Mbit / s or the like.

The switching call demultiplexing unit 314 shown in FIG.
Are the A subscriber IF 311, the I subscriber IF 312, and the L
The exchanged call 91 from the subscriber IF 313 is transmitted to a fixed band (64 k, 128 k,
1.5 Mbit / s, etc.) and an interface function between the newly provided xDSL data demultiplexing unit 323 shown in FIG. A free fixed bandwidth (1.5 M, 768 k, 384 kbit) different from the switched call 91 of the telephone subscriber 1
/ S, etc.) for each subscriber.
The switching call 91 and the data call 92 are STM-multiplexed (allocated to a fixed band determined in advance for each subscriber) and transmitted to the optical-to-electrical converter 315. 2 receives the STM-multiplexed signals of a plurality of subscribers from the optical-to-electrical converter 315, and outputs an A subscriber IF 311 and an I subscriber IF 312 corresponding to each subscriber. ,
It has the function of demultiplexing and transmitting to the L subscriber IF 313 and the xDSL data demultiplexing unit 323. Embodiments of the present invention thereby treat switched calls 91 and data calls 92 of xDSL subscriber 2 equivalent to switched calls 91 of telephone subscriber 1 with only minor changes to switched call demultiplexer 314. It becomes possible.

The optical-electrical converter 315 shown in FIG.
Receives the STM multiplexed electric signal from the switching call demultiplexing unit 314, converts the signal into an optical signal, and transmits the signal to the optical cable 8, and receives and terminates the STM multiplexed optical signal from the optical cable 8, It has the function of converting this into an electrical signal and transmitting it to the switched call demultiplexing unit 314.

The optical cable 8 shown in FIG. 1 connects the route distribution device 41 or the switching device 42 in the accommodation station 4 to the existing switching call processing unit 31 in the remote terminal device 3. The route distribution device 41 and the exchange device 42 shown in FIG.
The optical signal from the optical cable 8 is terminated, and the switched call 91 of the telephone subscriber 1 and the data call 9 of the xDSL subscriber 2 are STM-multiplexed.
2 is separated from each other by a TS unit, a subscriber unit, or the like. The separated switched call 91 is transmitted to the public / private line network 5, and the data call 92 is transmitted to the xDSL multiplexing device 43 installed in the accommodation station 4. The route distribution device 41 and the switching device 42 perform STM multiplexing on the exchange call 91 of the telephone subscriber 1 received from the public / private line network 5 and the data call 92 of the xDSL subscriber 2 received from the data network 6. Then, this is converted into an optical signal and transmitted to the optical cable 8.

The xDSL multiplexing device 43 shown in FIG. 1 has a function of processing a data call 92 from the xDSL subscriber 2 and connecting to the data network 6, and is a device newly installed in the accommodation station 4 according to the present invention. is there. As shown in FIG. 4, the xDSL multiplexing device 43 includes a route distribution device IF 431 and a switching device IF 432.
, A data call demultiplexing unit 433 and a data network IF 434
It is composed of

The route distribution device IF 431 and the switching device IF 432 shown in FIG. 4 terminate the signals from the route distribution device 41 and the switching device 42, and
It has a function to send and receive signals to and from the device. The data call demultiplexing unit 433 shown in FIG.
The data call 92 of each xDSL subscriber 2 received from the switch 31 and the switching device IF 432 is multiplexed, statistical multiplexing is performed, and the multiplexed data call 92 is transmitted to the data network IF 434. The data call demultiplexing unit 433 is connected to the data network IF
The data call 92 received from the 434 is separated, and the route distribution device IF 43 corresponding to the route in which each xDSL subscriber 2 is accommodated.
1 or to the exchange IF 432. In addition, each xDSL
The statistical multiplexing of data call 92 of subscriber 2 is shown in FIG.
xDSL data demultiplexing unit 323 in xDSL subscriber accommodation unit 32
May be performed. The data network IF 434 shown in FIG.
Has a data network terminating function, and has a data call demultiplexing unit 4
It has a function of transmitting and receiving data to and from the device 33.

Next, the switching call multiplexing / demultiplexing unit 314 in the existing switching call processing unit 31 shown in FIG. 2 and the route distributor 41 or the switching unit 42 in the accommodation station 4 shown in FIG. The multiplexing method of the switching call 91 and the data call 92 of the xDSL subscriber 2 will be described with reference to FIG.

A standardized SDH (Synchronous Digital Hiera) is provided between the accommodation station 4 and the remote terminal 3 shown in FIG.
A transmission path interface called “rchy (synchronous digital hierarchy)” or a simplified SDH is used. The simplified SDH is a partial simplification of various operational functions such as maintenance information and status monitor added when configuring a standard SDH, but has the same transmission format.
SDH includes STM-0 in which a maintenance frame for a network is added to a signal frame called VC-3 (virtual container-3) of about 50 Mbit / s, or VC
STM-1 (about 156 Mbit /
s) or STM-4 which is 4 times this STM-1
(About 600 Mbit / s). Each VC-3 has a VC-11 (virtual container) having 24 channels in 64 kbit / s conversion.
11; 1.5 Mbit / s).

The example used in the embodiment of the present invention shown in FIG. 5 is a VC-11 among three VC-3s of STM-1.
The data call 92 of the xDSL subscriber 2 and the switched call 91 of the telephone subscriber 1 are multiplexed and used. As described above, by assigning the data call 92 of the xDSL subscriber 2 to the free bandwidth of the fixed bandwidth (1.5 Mbit / s) allocated to the leased line subscriber, the route which is an existing device in the accommodation station 4 is assigned. It is possible to handle the same as the management of the conventional dedicated line subscriber without significantly changing the device management of the distribution device 41 or the switching device 42. The example shown in FIG.
The data call 92 of the xDSL subscriber 2 and the switched call 91 of the telephone subscriber 1 are multiplexed on a VC-11 basis.
64 kbit / s ch unit or VC in VC-11
It may be C-3 units, and is not particularly limited.

According to the embodiment of the present invention described above, a pair of optical cables 8 between the accommodation station 4 and the remote terminal 3
xDSL subscriber 2 data call 92 and telephone subscriber 1 exchange call 9
1 can be transmitted at the same time.

FIG. 6 is a block diagram showing the configuration of a switching system according to another embodiment of the present invention, which will be described below. 6, reference numeral 20 denotes a high-speed data subscriber; 33, a high-speed data subscriber accommodating unit; 44, a high-speed data multiplexing device; 73, an access line;
Is the same as

Another embodiment of the invention shown in FIG. 6 is a high-speed data subscriber 2 instead of a remote terminator 3 and an xDSL subscriber 2.
0, the access line 73 is not only copper wire, but also wireless,
Means for terminating and multiplexing / demultiplexing the access line 73 in the high-speed data subscriber accommodating unit 33 in the remote terminal device 3;
The accommodation station 4 is provided with a high-speed data multiplexing device 44 having a function corresponding to the xDSL multiplexing device 43 shown in FIG.

According to such another embodiment of the present invention, similarly to the case of the xDSL subscriber 2 in FIG.
A set of optical cables 8 between the accommodation station 4 and the remote terminal 3
In addition, the data call 92 of the high-speed data subscriber 20 and the switched call 91 of the telephone subscriber 1 can be simultaneously transmitted.

[0032]

As described above, according to the present invention, xDSL is provided on a pair of optical cables between a serving station and a remote terminal.
Since the data call of the subscriber or the high-speed data subscriber and the switched call of the telephone subscriber can be multiplexed, xDSL service or high-speed data transmission service can be provided to the subscriber under the remote terminal device. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a switching system according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration example of an existing switched call processing unit.

FIG. 3 is a block diagram illustrating a configuration example of an xDSL subscriber accommodation unit.

FIG. 4 is a block diagram illustrating a configuration example of an xDSL multiplexer.

FIG. 5 is a diagram illustrating an example of a multiplexing method of a data call of an xDSL subscriber and a switched call of a telephone subscriber.

FIG. 6 is a block diagram showing a configuration of a switching system according to another embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a switching system according to a conventional technology using an asymmetric digital subscriber line technology ADSL which is one of xDSL technologies.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Telephone subscriber 2 xDSL subscriber 2a ADSL subscriber 3 Remote terminator 4 Housing station 5 Public / private line network 6 Data network 11 A (analog) subscriber 12 I (ISDN) subscriber 13 L (private line) subscriber Reference Signs List 20 High-speed data subscriber 21 Telephone terminal etc. 22 Data terminal etc. 23, 23a Subscriber-side splitter 24, 24a Subscriber-side xDSL modem 31 Existing switched call processing unit 32 xDSL subscriber accommodating unit 33 High-speed data subscriber accommodating unit 41 Route Distributing device 42 Switching device 43 xDSL multiplexing device 43a ADSL multiplexing device 44 High-speed data multiplexing device 71 Copper wire 72 Copper wire / optical fiber 73 Access line 431a Station side splitter 432a Station side ADSL modem 433a Data demultiplexing section

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yumiko Nishi 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd.Communications Division (72) Inventor Yoichi Tsukioka 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd.Communications Division (72) Inventor Hironobu Kashiwagi, Kanagawa Prefecture, Yokohama, Japan 216 Totsuka-cho, Totsuka-ku, Yokohama, Japan Inside (72) Inventor Naomi Sugita 216 Totsukacho, Totsuka-ku, Yokohama, Kanagawa, Japan, Inc. F-term in the Hitachi, Ltd. Communications Division (Reference) CB04 CB05 CB08 DA06 EA19 EA30 FC02 FC17 FD02 FD03

Claims (4)

[Claims] 1. A switching system comprising a remote terminating device accommodating a telephone subscriber and an xDSL subscriber, a serving station, and an optical cable connecting the remote terminating device and the containing station.
The remote terminating device further comprises means for allocating a free fixed bandwidth different from a switched call from a telephone subscriber to a data call from an xDSL subscriber and performing STM multiplexing of the data call and the switched call, A switching system, wherein the accommodation station is provided with means for terminating the optical cable and separating the data call and the switched call multiplexed by a remote terminal device. 2. The accommodation station is connected to a data network, a public network, and a private network, and receives a data call from an xDSL subscriber received from the data network and a telephone subscription received from a public line network or a private line network. 2. The switching system according to claim 1, further comprising means for performing STM multiplexing with a switched call from a user and transmitting the multiplexed call to a remote terminal device via the optical cable. 3. A switching system comprising: a remote terminating device for accommodating a telephone subscriber and a data subscriber; a serving station; and an optical cable for connecting the remote terminating device and the containing station. Means for allocating a free fixed bandwidth different from a switched call from a telephone subscriber to a data call from a data subscriber and performing STM multiplexing of the data call and the switched call; And a means for terminating the data call and separating the data call and the switched call multiplexed by the remote terminating device. 4. The accommodation station is connected to a data network, a public network, and a private network, and receives a data call from a data subscriber received from the data network and a telephone subscription received from a public line network and a private line network. 2. The switching system according to claim 1, further comprising means for performing STM multiplexing with a switched call from a user and transmitting the multiplexed call to a remote terminal device via the optical cable.