JPH06350530A - Optical communication system - Google Patents

Abstract

PURPOSE:To specify the fault point of a line by providing optical parts at respective optical fiber lines so as to reflect light with a wavelength lambdai and to transmit light with wavelengths lambdao and lambdaj ((j) is integers to N, jnot equal to i). CONSTITUTION:The light with a wavelength lambda0 and the light with wavelength lambda1 is made incident to an optical fiber line I1, and the light with the wavelength lambda0 and the light with a wavelength lambda2 is made incident to an optical fiber line I2. The light with the wavelength lambda0 is light for communication, and the light with wavelengths, lambda1, lambda2...lambdai, lambdaj and lambdam is light for monitor so as to searching any fault. When a test wavelength is scanned within a range including these wavelengths in the case of moving a testing device OTDR installed at a station, the reflected light of lambda1, lambda2...lambdan reflected at optical parts D1, D2...Dn arranged at lines I1, I2...In is received from those lines. When any fault point exists at the line I1, the fault point can be specified since the OTDR observes any loss change in the reflected light with the wavelength lambda1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical communication system,
More specifically, the present invention relates to an optical communication system capable of monitoring a failure of each optical line used by a system subscriber for all optical lines.

[0002]

2. Description of the Related Art Currently, a PDS (Passiv) as shown in FIG.
An optical communication system called "e Duble Star" is regarded as a promising one that will reduce the economic burden on system subscribers. In this system, first, an optical communication terminal A is installed in a station, an optical fiber line ₁₀ is laid outside the station, and the optical communication terminal A is connected to an optical branching / coupling device B.

This optical branching / coupling device B is usually composed of 8 or 16 units.
It has a plurality of (N) branches such as a book and 32 branches. The optical fiber line l is provided in the first branch 1.
_1, so that the optical fiber line l ₂ is that the second branch 2, generally i-th in the branch i optical fiber line l _i
Are connected N times. Each of the optical fiber line _{l 1, l 2, ...... l} i, the ...... l _N, an optical communication terminal system subscriber's _{C 1, C 2, ...... C} i, ...... C N
Are connected respectively.

In this system, the communication light emitted from the optical communication terminal A of the station and having the wavelength λ ₀ propagates through the optical fiber line l ₀ and is input to the optical branching / coupling device B, where N The distributed light for communication, which is distributed to the branches of the book, propagates through the optical fiber lines l _i (i = 1, 2, ... N) and the respective optical communication terminals C of the respective system subscribers.
_i (i = 1, 2, ... N) is received.

In the case of this system, the equipment costs of the optical communication terminal C _i owned by the system subscriber and the optical fiber line l _i up to the optical branching / coupling device B are, of course, borne by the individual subscribers. It However, since the optical fiber line l ₀ from the station to the optical branching / coupling device B is shared by all the system subscribers, the load per subscriber is reduced.

[0006]

By the way, in the existing optical line monitoring system currently put into practical use, an OTDR is usually incorporated as a test device. This O
TDR is a device that measures the weak reflected light observed over the entire length of the installed optical fiber line as a function of the propagation time of light. The observed reflected light level is defined by the optical loss, and the propagation time is defined by the position in the longitudinal direction of the optical fiber line. Therefore, in this OTDR, the optical loss due to, for example, breakage is eventually expressed as a function of the position. Can be measured.

In the optical line monitoring system incorporating this OTDR, the longitudinal distribution of the optical fiber loss is periodically measured after laying the optical fiber line, and the measured data is compared with the data before the laying. The change in loss due to the occurrence of a failure and the position of the failure point are specified. However, if the OTDR is applied to the system shown in FIG. 4, the following inconvenience occurs.

That is, when the OTDR is incorporated into the system shown in FIG. 4, the OTDR is installed at a station. Therefore, the reflected lights from all the optical fiber lines l _i are collectively incident on the OTDR installed in the station. Therefore, when a failure occurs on a subscriber side on the downstream side of the optical branching / coupling device B, the reflected light from the failure point and the reflected light from the optical line in which no failure has occurred are combined. Since it is incident on the OTDR, it is not possible to specify which optical line is the obstacle.

Further, the change in loss due to a failure becomes as small as 1 / the number of optical fiber lines (N), and there is a problem that its detection is extremely difficult. The present invention solves the above-mentioned problem when the OTDR is incorporated into the PDS system shown in FIG. 4, and specifies the failure point even if any of the optical fiber lines on the system subscriber side fails. It is an object of the present invention to provide an optical communication system that can be used.

[0010]

[Means for Solving the Problems] To achieve the above object.
Therefore, in the present invention, the optical communication terminal A and the optical communication terminal
Optical fiber line l connected to the signal terminal A₀And the light
Fiber track l₀Connected to the optical component with multiple branches
The branch coupler B is connected to each branch of the optical branch coupler.
Optical fiber line 1 to be connected to the optical fiber line 1 and
Optical communication including optical communication terminal C connected to each
In the system, each of the optical fiber lines 1
Is the wavelength λ_iThe light of (i = 1, 2, ... N) is reflected,
One, wavelength λ ₀And wavelength λ_j(J = 1, 2, ... N, just
However, the optical component D that transmits the light of j ≠ i) is arranged.
An optical communication system characterized by the above is provided.

An outline of the optical communication system of the present invention is shown in FIG.
You As is apparent from FIG. 1, the optical communication system of the present invention
In the PDS system shown in FIG.
Optical communication terminal C of the resident₁, C₂, …… C_i, …… C_NContact with
Each successive optical fiber line l₁, L₂, ……
l_i, …… l_NOptical component D described later in₁, D₂, ……
D _i, …… D_NIs arranged.

The optical components D ₁ , D ₂ , ... D _i , ... D
_N is light for all at the wavelength lambda _i test reflects, but light for communication of light and the wavelength lambda ₀ of the test other than the wavelength lambda _i are those that pass through, specifically, , A filter component composed of a dielectric multilayer thin film.

[0013]

In this optical communication system, the optical fiber line
Road l₁Has the wavelength λ₀Light and wavelength λ₁Light is incident on the
Fiber line l₂Has the wavelength λ₀Light and wavelength λ₂The light of
Generally, the i-th optical fiber
Railroad l_iHas the wavelength λ₀Light and wavelength λ_iThe light of
j-th optical fiber line l_jHas the wavelength λ₀Light and wavelength λ
_jLight is incident and the last optical fiber line l_NTo the wavelength
λ₀Light and wavelength λ _NLight is incident. Where wavelength λ
₀Light is for communication and has wavelength λ₁, Λ ₂, ……
λ_i, …… λ_j, …… λ_NThe light of to search for obstacles
Monitor light. And the wavelength λ₁, Λ₂, …… λ_i，
...... λ_j, …… λ_NAre different from each other
There is. That is, λ_i≠ λ_jIs.

Therefore, the OTDR installed at the station is now
In operation, the test wavelength should include the wavelengths listed above.
When scanning within the range, each optical fiber line l₁，
l₂, …… l_i, …… l_NFrom those fiber optic lines
Optical component D placed on the road ₁, D₂, …… D_i, ……
D_NWavelength λ reflected at₁, Λ₂, …… λ_i, …… λ_Nof
Only reflected light can be received.

Therefore, for example, the optical fiber line l ₁
If there is a fault in the OTDR, the wavelength λ
_{Since the} change in the loss of the reflected light of ₁ is observed, it is possible to identify the failure point.

[0016]

EXAMPLES In the Figure 1 system, an optical communication terminal wavelength as A lambda _0: set up a single mode optical fiber transmitter for transmitting light of 1.3 .mu.m, this wavelength lambda ₀ as the optical fiber line l _0: A single mode optical fiber that propagates 1.3 μm light was connected. In this single mode optical fiber l ₀ , 1
An input / eight-branch optical branching coupler B was connected, and each branch was connected with a single-mode optical fiber l ₁ , l ₂ , ... L ₈ for propagating light having a wavelength λ ₀ : 1.3 μm.

Then, the optical component D as shown in FIG.
_i (i = 1, 2, 3, ... 8) was prepared. This optical component D _i is made of, for example, quartz glass in a silica glass clad 1 formed by flame deposition and photolithography on a Si single crystal substrate, and has a path width of 8 μm.
A straight waveguide 2 with a relative refractive index difference Δ: 0.3% is embedded with a path height of 8 μm, and a band-pass filter 3 having a dielectric multilayer thin film structure is arranged orthogonally to the longitudinal direction of the straight waveguide 2. Is.

This filter 3 has a wavelength λ _i (i = 1,
Light of 2, ... 8) is transmitted, but wavelength λ ₀ (1.
3 μm) and wavelength λ _j (j = 1, 2, ... 8, where j
Light of ≠ i) is manufactured to pass. A single-mode optical fiber l _i is connected to one end face of the optical component D _{i with} the linear waveguide 2 aligned with the optical axis, and the other end face also receives light of wavelength λ ₀ : 1.3 μm. A single-mode optical fiber l' _i for propagation is connected to the linear waveguide 2 with its optical axis aligned.

Then, each single mode optical fiber l '₁， L '
₂、 …… l '_i、 …… l '_NHas wavelength λ₀: 1.
Single-mode fiber optic receiver for receiving 3 μm light
C₁, C ₂, …… C_i, …… C_NConnect the light of the present invention
It was a communication system. In this system, the station is OT
DR is installed and the test wavelength is λ₀And λ₁, Λ
₂, Λ₃, Λ_Four, Λ_Five, Λ₆, Λ₇, Λ₈To cover
When you scan in the range, the display waveform of OTDR is shown in Figure 3.
It became a pattern.

That is, in the longitudinal direction of the optical line, O
The loss distribution from the point to the point b where the optical branching / coupling device B is installed is based on the reflected light of the single mode optical fiber l ₀ , and from the point b to the optical component D _i (i = 1). ，
The loss distributions up to point d at the positions where 2, 3, ... 8) are installed are all single mode optical fibers l _i (i = 1, 1).
It is based on the reflected light of 2, 3, ... 8). The loss distribution at the position on the right side of the point d is based on the reflected light from the single mode optical fiber selected from the single mode optical fibers l ₁ , l ₂ , ..., L ₈ .

Therefore, by observing the change in the displayed waveform, it is possible to specify at which position the failure has occurred.

[0022]

As is apparent from the above description, in the optical communication system of the present invention, even if the OTDR is incorporated in this system, a plurality of optical branching couplers are connected to the optical communication terminals of system subscribers. It is possible to identify a fault point of the optical fiber line of the book. This means that the test light of one wavelength is reflected on each of the optical fiber lines connecting the optical communication terminal of the system subscriber and the optical branching / coupling device, but the other test light and communication light are transmitted. This is the effect brought about by arranging the optical components that perform.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an optical communication system of the present invention.

FIG. 2 is a plan view showing an example of an optical component incorporated in the system of the present invention.

FIG. 3 is a graph showing an example of a display waveform of an OTDR incorporated in the system of the present invention.

FIG. 4 is a schematic diagram showing an example of a conventional optical communication system.

[Description of Reference Signs] A optical communication terminal B optical branching / coupling device C ₁ , C _i , C _N system subscriber optical communication terminal D ₁ , D _i , _DN optical component l ₀ optical fiber line l ₁ , l ′ ₁ , L _i , l' _i , l _N , l' _N Optical fiber line 1 Quartz clad 2 Quartz straight waveguide 3 Bandpass filter

Claims (1)

[Claims] 1. An optical communication terminal A, an optical fiber line l ₀ connected to the optical communication terminal A, and the optical fiber line l.
An optical branching / coupling device B connected to ₀ and having N branches,
In an optical communication system including an optical fiber line l connected to each branch of the optical branching coupler and an optical communication terminal C connected to the optical fiber line l, each of the optical fiber lines l Has the wavelength λ
The light of _i (i is an integer up to N) is reflected and the wavelength λ ₀
And wavelength λ _j (j is an integer up to N, where j ≠ i)
An optical communication system characterized in that an optical component D for transmitting the light is disposed.