JPH11127153A - Transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure variations of information that is sent to user terminal by sending incoming/outgoing two-way 1st information, via the time base compressed multiplexing using the prescribed wavelength and then sending 2nd information in the outgoing direction via the wavelength multiplexing in a band which does not include prescribed wavelength. SOLUTION: A fast SLT 32 connected to an MUX 31 is connected to an 8-branched star coupler 34, via an optical fiber 33 at a remote station. A transmission system 30 is secured in an incoming/outgoing two way transmission band, where an asymmetrical band of up directions of 34 and 56 Mbps and outgoing direction of 96 Mbps is allocated. A band of incoming direction of 3 Mbps and outgoing direction of 9 Mbps is secured for every subscriber, and the subscriber receives a digital images of 1ch and also receives the two way digital signal transmission service in the remaining band. When the transmitting 60ch analog video signals are required in a frequency division multiplex subscriber transmission system 15, the subscriber selects his desired 1ch via a WDM 35A and a V-ONU 18 and performs the frequency division multiplex analog TV signal distribution service, without using the wavelength multiplexing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network in a PDS (passive double star)
The present invention relates to a transmission method suitable for performing optical access in a TM (asynchronous transfer mode).

[0002]

2. Description of the Related Art In a conventional optical access system, an ATM transmission system is known as a technology for transmitting high-speed digital information such as a moving image in addition to low-speed digital information. A
In the TM transmission method, various types of information are transmitted in units of cells, not in units of information rates, so that telephones, data signals, and images are all transmitted in units of cells regardless of the information transmission speed and frequency.

[0003] A PDS system has been proposed in order to use the ATM transmission system together with the subscriber line in an economical manner. In this PDS system, the subscriber line has a structure in which an optical fiber is branched in a tree shape, and there is no active element consuming power in the middle. The optical fiber is connected to an ONU (optical subscriber line network device) at a subscriber's house that converts a signal received via the optical fiber into an electric signal. Therefore, the subscriber line is highly resistant to the environment and is economical.

An optical subscriber transmission system employing the PDS system is described in the following document 1.

Reference 1 "Development of Optical Subscriber Transmission System in NTT" Author Hisao Tsuji, Hiromichi Shinohara, Shigeru Rouki Source: IEICE Technical Report CS (OCS) 92-1 FIG. This is a configuration of the subscriber transmission system 9. In this system, the wavelength is 1.3.
In μm, bidirectional transmission is realized by the TCM (time axis compression multiplex) method. Further, the TV signal distribution system 15 frequency-division multiplexed by wavelength multiplexing (wavelength 1.5 μm) is coupled to share the line equipment.

In FIG. 2, a narrow-band, ie, low-speed, optical network unit N-SLT 11 which connects an information transmission line to a MUX (multiplexer) 10 at a remote station is passively connected via an optical fiber 12. Star coupler consisting of elements 1
The star coupler 13 is connected to a narrow band, that is, a low-speed optical subscriber line network device N-ONU 14 in the user's home.

[0007] The N-SLT 11 and the N-ONU 14 each include a wavelength multiplexing unit WDM 11A, 14A.

In the frequency division multiplexing subscriber transmission system 15 shown by a dashed line in FIG. 2, a remote station, at a remote station, a video SLT, such as a buffer and an E / O converter, that is, a V-SLT 16 And this V-SLT1
6 is a video source 17 for providing a video source to the user's home, and is a video ONU, ie, a V-ONU 18
It is.

[0009] V- supplied with a video source by an electric signal
The SLT 16 converts a video source into an optical signal and converts the signal into an N-SL.
It transmits to WDM of several N-SLTs, such as T11. Upon receiving this, the WDM in the N-SLT such as the WDM 11A transmits the optical signal to the N-O at each user home such as the N-ONU 14.
The signal is transmitted to the NU, and the optical signal reaches the V-ONU 18 via the WDM in the N-ONU.

In FIG. 2, the specifications of the low-speed digital optical subscriber transmission system 9 are as follows: wavelength used: 1.3 μm transmission distance: usually 7 km Maximum number of branches: 16 branches Transmission speed: about 28 Mbps Bidirectional multiplexing: TCM

In FIG. 2, the specifications of the frequency division multiplexing optical subscriber transmission system 15 are as follows: wavelength used: 1.55 μm, number of branches: 16000 or more.

On the other hand, in the PDS optical subscriber system, A
AT by optical access to provide TM service
An example of studying the M-PDS transmission scheme is described in the following reference 2.

Reference 2 “ATM based Passive Double”
Star system offering B-ISDN, N -ISDN, and POT
S "Author Yoshihiro Takigawa, Shin'ichi Aoyagi, and Ei
ji Maekawa Source GLOBCOM '93 (Dec. 1993) This ATM-PDS transmission system 19 is shown in FIG. In FIG. 3, the optical signals POT-NW and N-ISD
The SLT 22 having the N20 and the B-ISDN 21 connected to the IFs 22A and 22B outputs the narrow band POT-NW of the optical signals formatted by the IFs 22A and 22B.
And N-ISDN are converted to a wide band by CONV22C, while B-ISDN is kept as it is, and PDS / LT22D
To the star coupler 23.

The optical signal is supplied from the star coupler 23 to the ONUs 25 to 27. For example, in the ONU 25, the optical signal is sent to the CONV via the PDS LT 25A.
25B, and converted into a narrow band again by CONV25B.

The signal converted to the narrow band is ONU2
5 corresponding to each of the CHs 25C and 25D, and is extracted from each of the interfaces 25E and 25F as an N-ISDN, that is, a low-speed digital information signal. O on the reverse route
A digital information signal can be transmitted from the NU 25.

As this digital information signal, high-speed digital information including digital video information as well as low-speed digital information such as a telephone signal POT can be transmitted and received.

That is, the above ONU depends on the subscriber's request.
25 sets of POT and N-ISDN can be combined into one set of POT and N-ISDN and B-ISDN, or two B-ISDNs.
It can be replaced by ISDN. An example is ONU2
6 and 27.

ATM-PDS transmission system is B-ISD
Since conversion is based on N, conversion by a CONV is not performed on a broadband optical signal.

The specifications of the ATM-PDS transmission system 19 are as follows: wavelength used: 1.3 μm upstream, 1.55 μm downstream Transmission distance: maximum 10 km Number of branches: 16 branches Transmission speed: 155.52 Mbps Bidirectional multiplexing: WDM

The main features of this ATM-PDS transmission system 19 are up-down bidirectional transmission by wavelength division multiplexing, transmission speed 1
55.52 Mbps, the maximum number of branches by PDS is 16, and the distance between the station and the subscriber is 10 km at the maximum.

ATM-PD described in the above reference 2
FIG. 4 shows the S transmission frame format. In FIG. 4, the time slot numbers indicated by ♯ are: ♯1 to ♯256: for user signals ♯257 to ♯272: for OAM (control management) of 16 ONUs. The reason why # 257 to # 272 are used for OAM is that each (up to) 16 ONUs branched from the passive star coupler requires one OAM cell per 1 ms.

In FIG. 4, the period of one frame is set to 1 ms for both the upstream (upstream) and the downstream (downstream). This is because the transmission efficiency increases, but on the other hand, the transmission efficiency cannot be made longer than 1 ms in order to determine the transmission timing of the upstream burst signal for all of the 16 ONUs and not to lower the service quality.

1 PDS cell length is 60 per frame 1 ms
Since it is a byte, 324 PDS cells are accommodated in one frame.

In the PDS configuration, since it is necessary to control the upstream signal so as not to collide with the star coupler, which is a passive device, it is necessary to measure the transmission distance between the station and each subscriber during setup. In this system, the maximum distance between the station and the subscriber (between the ONU and the SLT) is 10 km, so a round-trip time of about 20 km (approximately 100 μs or more) is prepared in one frame for a round trip to measure the transmission distance. I have.

After all, one upstream frame is stored in the user area 25.
6 cells, 16 cells in the OAM area, and 52 cells in the transmission distance measurement area. Similarly, one downlink frame has 256 cells in the user area, 16 cells in the OAM area, and an area corresponding to the upstream transmission distance measurement area has a not spec.
ififed.

[0026]

SUMMARY OF THE INVENTION By the way, CATV
(Cable TV), VOD (Video on Demand), etc., the transmission speed required for digital video distribution services from subscribers to subscribers is up to 6 Mbps for NTSC level images, assuming MPEG2 encoding. It is about.

Therefore, if the above-described frame configuration is used in the above-described ATM-PDS system 19, the user area is 256 cells, and the bandwidth per subscriber is 6 Mbps (16 PDS cells) in consideration of the maximum branch (16). ), The provision of one channel of video service to each subscriber is limited.

In addition, since bidirectional transmission is realized by wavelength division multiplexing, there is a problem that an analog TV (television) signal distribution system having a wavelength of 1.5 μm, which is currently widely used, cannot be provided to users.

[0029]

According to a first aspect of the present invention, there is provided a transmission method for performing bidirectional uplink and downlink information transmission between a single station device and a plurality of user terminals. In the above, the first information service is provided by transmitting the first information in the up-down direction in the time axis compression multiplexing using the predetermined wavelength, and the second information is provided in the band not including the predetermined wavelength. The second information service is provided by wavelength multiplexing the above information and transmitting it in the downlink direction.

According to the second aspect of the present invention, the upstream direction is narrowed between a single device on the station side and a plurality of user terminals via the optical transmission line between the single device on the office side and the plurality of user terminals via the star coupler having the passive double star configuration. In a transmission method of performing bidirectional information transmission in a downstream direction in a wide band, digital information is transmitted in both directions up and down the optical transmission line by time-axis compression multiplexing using a predetermined wavelength, and supplied from an external system. The single station-side device that receives the analog video signal wavelength-multiplexes the analog video signal in a band that does not include the predetermined wavelength and supplies the multiplexed analog video signal in the downstream direction.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION

(A) Embodiment In the present embodiment, the maximum number of branches is set to 8, but each subscriber (upstream and downstream bandwidth), which is a characteristic of the video distribution service, is used by utilizing the asymmetry of the upper and lower transmission bands. User), a bidirectional digital signal transmission service is provided in addition to the digital video service 1ch, and furthermore, these bidirectional transmissions are realized by a TCM using a 1.3 μm wavelength, so that a 1.5 μm analog TV signal is provided. It is characterized in that distribution service can be provided together.

(A-1) Configuration of the Embodiment In FIG. 1 showing the configuration of the ATM-PDS transmission system 30 according to the present embodiment, the structure of the system is similar to the PDS transmission system 9 of FIG. In this system 30, the structure of each line and each device is adapted for high-speed optical access in order to perform high-speed optical access of 155.52 Mbps.

In FIG. 1, a high-speed SLT 32 connecting an information transmission line to a MUX 31 at a remote station is an 8-branch star coupler 3 composed of passive elements via an optical fiber 33.
4, the star coupler 34 is connected to a high-speed ONU 35 in the user's house ahead. Eight ONUs including the ONU 35 can be connected to the star coupler 34.

Both the SLT 32 and the ONU 35 have built-in wavelength multiplexing units WDMs 32A and 35A. Also, S
The distance between an installed station such as the LT 32 and an ONU such as the ONU 35 (subscriber) is 10 km at the maximum.

The specifications of the ATM-PDS transmission system 30 are summarized as follows: wavelength used: 1.3 μm (ATM signal), 1.55 μm
(CATV signal) Transmission distance: Up to 10 km Number of branches: 8 Branch Transmission speed: 155.52 Mbps Bidirectional multiplexing: TCM Band: 34.56 Mbps (up), 96.00 Mbps
(Down).

The frequency division multiplex subscriber transmission system 15 provided in the ATM-PDS transmission system 30 and shown by a dashed line in FIG. 1 is the same as the frequency division multiplex subscriber transmission system 15 of FIG. The same reference numerals are given to the portions, and the detailed description is omitted.

The operation of this embodiment having the above configuration will be described below.

(A-2) Operation of the Embodiment In the transmission system 30, the transmission band in the upper and lower
It is asymmetrical by allocating a wide bandwidth in the downstream direction to 96.00 Mbps downstream from 4.56 Mbps.

A frame used for information transmission in the transmission system 30 has a configuration as shown in FIG.

In FIG. 5, one frame is 1 ms (= 19
440 bytes). Maximum distance between station and subscriber is 10k
m, the transmission distance measurement area (Deley
measurement area: 3120 bytes) 52 cells and Upstream frame area: 4320 bytes
s) 72 cells, downstream transmission area (Downstream frame area:
12000 bytes) 200 cells are allocated.

The DMR is a transmission distance measurement request cell transmitted from the SLT 32 to the ONU 35, and the DMI is
This is a transmission distance measurement response cell transmitted from the ONU 35 in response to R. S measured in the DMR just before 1 ms
It is preferable to include transmission distance information from the LT 32 to the ONU 35. This DMI is received by the SLT 32 with a delay of the round trip time from the transmission point of the DMR.

Thereafter, C1 to C1 transmitted from the ONU 35
A cell such as C3 includes an upstream frame (Upstream) together with cells from the other seven ONUs connected to the star coupler 34.
frame) and are forwarded further upstream as needed. In the uplink frame, cells C1, C
2. The cells from the other seven ONUs can enter the blank area on the left of C3.

For example, when requesting the provision of a digital video service such as VOD, the subscriber uses the ONU 35 to transmit a cell (upstream frame) such as the cell C1 to the SLT 32. Upon receiving this, the SLT 32 provides the digital video to the ONU 35 in the leftmost cell CA of the downstream frame (Downstream frame) in FIG. Similarly, ONU35
The other seven ONUs also have cell C at the same time as ONU 35.
Digital information services such as digital video can be provided in cells in downstream frames such as C.

That is, according to the frame configuration shown in FIG.
3 Mbps in the upstream direction and 9 Mbps in the downstream direction per subscriber
ps bandwidth, each subscriber will receive digital video 1c
In addition to receiving h, it is possible to receive a bidirectional digital signal transmission service in the remaining band.

On the other hand, an analog video signal (60 ch) transmitted from the frequency division multiplex subscriber transmission system 15
Is obtained without using a cell as shown in FIG.
The subscriber via the WDM 35A is constantly transmitting 6
The V-ONU 18 only needs to select the desired 1ch from the 0ch analog TV signal.

That is, since wavelength multiplexing is not used for bidirectional transmission, an analog TV signal distribution service which is frequency division multiplexed using a wavelength of 1.5 μm can be provided.

(A-3) Effects of Embodiment As described in detail above, in this embodiment, the star coupler 34
Has the maximum number of branches, but the conventional ATM-
As in the PDS transmission system, not only can digital video services be provided to subscribers, but also the effect of providing frequency-division multiplexed analog TV signal distribution services by wavelength multiplexing can be obtained.

(B) Other Embodiments In the above description, a passive double star configuration is used. However, an active type or a single star type may be used as necessary. Also, there is no need to limit to the ATM system.

In the above description, the maximum number of branches has been described as 8. However, the maximum number of branches and other specifications may be changed in accordance with various conditions, such as MPEG2 and the maximum transmission distance.

[0050]

As described above, according to the first aspect, it is possible to secure a variety of information that can be provided to a plurality of user terminals.

According to the second aspect of the present invention, not only can digital information be transmitted in both directions up and down, but also analog television signals can be supplied to the user terminal at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an ATM-PDS transmission system according to an embodiment.

FIG. 2 is a block diagram showing a conventional PDS transmission system.

FIG. 3 is a block diagram showing a conventional ATM-PDS transmission system.

FIG. 4 is a schematic diagram showing a conventional ATM-PDS frame configuration.

FIG. 5 is a schematic diagram showing an ATM-PDS frame configuration according to the embodiment.

[Explanation of symbols]

10, 31,... MUX, 11, 16, 22, 32,.
T, 14, 18, 25-27, 35 ONU, 15 frequency division multiplex subscriber transmission system, 19, 30 ATM
A PDS transmission system.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H04J 3/00 H04L 11/00 340 H04L 12/44 11/02 D 12/02

Claims (3)

[Claims] 1. A transmission method for transmitting information in a bidirectional manner between a single device on a station side and a plurality of user-side terminals, comprising: a time axis compression multiplex using a predetermined wavelength; First
The first information service is provided by performing the transmission of the second information, and the second information is wavelength-multiplexed and transmitted in the downstream direction in the band not including the predetermined wavelength to thereby obtain the second information. A transmission method characterized by providing a service. 2. The transmission method according to claim 1, wherein the first information is digital information, and the second information is analog information. 3. An optical transmission path between an apparatus on a station side and a plurality of user terminals via a star coupler having a passive double star configuration has a narrow band in the upstream direction and a wide band in the downstream direction. In the transmission method for performing bidirectional information transmission, digital information is transmitted up and down the optical transmission line by time-axis compression multiplexing using a predetermined wavelength, and an analog video signal supplied from an external system is received. A transmission method, wherein a single device at the station side wavelength-multiplexes the analog video signal in a band not including the predetermined wavelength and supplies the multiplexed video signal in the downstream direction.