JPH02282228A - Optical tap - Google Patents

Abstract

PURPOSE:To obtain the optical tap which compensates an optical branching loss with simple constitution and can increase the number of tap points in a transmission system by multiplexing stimulating light and wavelength light of 1.5mum band with an optical star coupler, then making one branched light ray thereof to a rare earth element-added optical fiber amplifier. CONSTITUTION:The wavelength light of 1.5mum band emitted from a light source 1 arrive via an optical tap 10 and is multiplexed light is branched to two rays. Of the branched light rays, the one is made incident to the optical fiber amplifier 13 and is put into the exciting state by the incidence of the exciting light, by which the wavelength light of 1.5mum band is subjected to an amplification effect. The light loss by the optical fiber 2 and the optical branching loss by the optical star coupler 12 of the wavelength light of 1.5mum band are compensated by this amplification effect. This light is transmitted to the optical fiber 4. The only the wavelength light of 1.5mum band of the other branched light ray by the optical star coupler 12 is passed by the optical filter 12 and the exciting light is shut off so that only the wavelength light of 1.5mum band is received by a photodetecting element 22.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical tap used in optical LANs and the like, for branching and extracting signal light midway through a transmission path.

(Prior Art) FIG. 2 is a block diagram of an optical fiber transmission system using a conventional optical tap.

In Figure 2, 1 is a 1.5 μm band light source, and 1°5 μm band light source.
It emits light with a wavelength of (1,51=1.57 μm).

Reference numeral 2 denotes an optical fiber for a transmission line, through which light having a wavelength of 1.5 μm from the light source 1 is propagated. 3 is an optical tap, which is composed of a 2x2 optical star coupler 3a.

This optical star coupler 3a inputs wavelength light in the 1.5 μm band propagated through the optical fiber 2 into one input end, branches it into two, taps one branched light, and outputs it from one output end. , the other branched light is emitted to the next-stage transmission line optical fiber 4 from the remaining emitting end. 5 is a light receiving element that receives the tap output from the optical tap 3;

In such a configuration, 1, emitted from the light source 1,
After the wavelength light in the 5 μm band is transmitted through the optical fiber 2, it enters one input end of the optical star coupler 3a and is split into two. Among these branched lights, one branch destination is emitted from one output end, propagated to the next stage transmission line optical fiber 4, and received by the light receiving element 5. On the contrary,
The other branched light is output from the remaining output end as a tap output.

(Problem to be solved by the invention) However, in the above-mentioned conventional optical tap, since the wavelength light power in the 1.5 μm band for each optical tap suffers optical branching loss at the 2×2 optical star coupler 3a, the transmission system The disadvantage is that the number of tap points is limited.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical tap that has a simple configuration, can compensate for optical branching loss, and can increase the number of taps in a transmission system. It is in.

(Means for Solving the Problem) In order to achieve the above object, claim (1) provides an excitation light source that emits excitation light, and a wavelength in the 1.5 μm band that is transmitted with the excitation light through an optical fiber. an optical star coupler that multiplexes light, branches the combined light, and outputs the combined light; and a rare earth element-doped optical fiber amplifier that receives one branched light of the optical star coupler and amplifies the wavelength light in the 1.5 μm band. Equipped with.

Further, in claim (2), an excitation light source that emits excitation light and a combined light of the excitation light and wavelength light in the 1.5 μm band transmitted via an optical fiber are input, A rare-earth element-doped optical fiber amplifier that amplifies the wavelength light, and a 1.5 μm wavelength light amplified by the rare-earth element-doped optical fiber amplifier.
combining m-band wavelength light and excitation light from the excitation light source;
and an optical star coupler that branches and emits the combined light.

(Function) According to claim (1), the wavelength light in the 1.5 μm band transmitted through the optical fiber and the excitation light from the excitation light source are input to the optical star coupler and combined. The optical star coupler branches this combined light into two, for example, and outputs the branched light.

Next, one of these branched lights is input to a rare earth element-doped optical fiber amplifier.

As a result, the rare earth element-doped optical fiber amplifier becomes excited and amplifies the wavelength light in the 1.5 μm band. This amplification effect compensates for optical loss due to the optical fiber and optical branching loss due to the optical star coupler. Next, the amplified wavelength light in the 1.5 μm band is sent to the next stage optical fiber for the transmission line.

On the other hand, the other branched light by the optical star coupler is
It is emitted as a tap output and received at the tap point.

According to claim (2), the combined light of the excitation light and the wavelength light in the 1.5 μm band transmitted through the optical fiber is input to the rare earth element-doped optical fiber amplifier. As a result, the rare-earth element-doped optical fiber amplifier becomes excited and 1
．． Amplifies wavelength light in the 5 μm band. Due to this amplification effect,
Optical loss due to the optical fiber and optical branching loss due to the optical star coupler in the next stage are compensated for.

Next, the amplified light in the 1.5 μm band enters the optical star coupler and is combined with the excitation light from the excitation light source. The optical star coupler branches this combined light into two, for example, and outputs the branched light.

Next, one of these branched lights is sent to the next-stage transmission line optical fiber.

On the other hand, the other branched light by the optical star coupler is
It is emitted as a tap output and received at the tap point.

(Embodiment) FIG. 1 is a block diagram showing a first embodiment of an optical fiber transmission system using an optical tap according to the present invention, and the same components as in FIG. 2 showing the conventional example are denoted by the same reference numerals. It is expressed as. That is, 1 is a 1.5 μm band light source, and 1.5 μm band (1,51~
It emits light with a wavelength of 1,57 μm). Reference numeral 2 denotes an optical fiber for a transmission line, through which light having a wavelength of 5 μm is propagated.

]O is an optical tap, which is composed of a pumping light source 11, a 2×2 optical star coupler]2, and a rare earth element-doped optical fiber amplifier 13.

For example, the excitation light source 11 has an oscillation wavelength of 1.48 μm band (]
,, consists of a semiconductor laser with a diameter of 441 to 1.49 μm, and emits excitation light at a predetermined intensity (several tens of mW).

The 2x2 optical star coupler 12 connects the excitation light source 11 with the 1.5 μm band wavelength light propagated through the optical fiber 2 at one input end.
The excitation light is incident on each of the remaining input ends and combined, and the combined light is split into two and output from the two output ends.

The rare earth element-doped optical fiber amplifier (hereinafter referred to as an optical fiber amplifier) 13 is constructed by doping an optical fiber with a rare earth element, for example, erbium (hereinafter referred to as Er) at a predetermined concentration. This optical fiber amplifier 13 is
One end of the branched light is connected to one output end of the optical starch coupler 12, and the other end is connected to one end of the optical fiber 4 for transmission line.
The m-band wavelength light is amplified and sent to the optical fiber 4.

21 is an optical filter which receives the other branched light from the optical star coupler 12 and transmits only the wavelength light in the 1.5 μm band, and filters out other wavelength light, that is, excitation light in the 1.48 μm band and natural light. Block out light.

22 is a light receiving element, and the 1.5μ light transmitted through the optical filter 21 is
Receives m-band wavelength light.

Next, the operation of the above configuration will be explained.

Light having a wavelength of 1.5 μm emitted from the light source 1 is sent to an optical fiber 4 . 1 propagated through this optical fiber 4
, 5 μm band wavelength reaches the optical tap 10, enters one input end of the optical star coupler 12, and is split into two.

On the other hand, the excitation light in the wavelength band of 1.48 μm from the excitation light source 11 is incident on the remaining input end of the optical star coupler 12 . The optical star coupler 12 combines these incident lights, splits the combined light into two, and makes one of the branched lights enter one end of the optical fiber amplifier 13 .

The optical fiber amplifier 13 is brought into an excited state by the incidence of the pumping light, and as a result, the wavelength light in the 1.5 μm band is amplified. Due to this amplification effect, the wavelength light in the 1.5μ band is reduced by the optical loss due to the optical fiber 2 and the optical star coupler]
Optical branch loss due to 2 is compensated for. Next, the amplified wavelength light in the 1°5 μm band is sent to the next stage optical fiber 4 for the transmission line.

On the other hand, the other branched light by the optical star coupler 12 is output as a tap output and is input to the optical filter 21. The optical filter 21 transmits only wavelength light in the 1.5 μm band, and blocks excitation light and spontaneously emitted light from the optical fiber amplifier]3.

Thereby, the light receiving element 22 receives only the wavelength light in the 1.5 μm band, converts it into an electrical signal, and then processes it by a processor (not shown).

As described in Section 1 below, according to the embodiment of Section 1, the wavelength light in the 1.5 μm band transmitted through the optical fiber 2 and the excitation light from the excitation light source 11 are combined by the optical star coupler 12. Then, this combined light is split into two, one branched light is amplified by an optical fiber amplifier 13, and then sent to the next optical fiber 4, and the other branched light is tapped by an optical star coupler 12. Since the configuration is configured so that the output is output, the optical loss due to the optical fiber 2 and the optical branching loss due to the optical star coupler 12 can be compensated for with a simple configuration, and the number of tap points in the system can be increased. Tap is realized.

FIG. 3 is a configuration diagram showing a second embodiment of an optical fiber transmission system using an optical tap according to the present invention.

The difference between the embodiment of Section 2 and the first embodiment is that an excitation light source 23 similar to the excitation light source 11 and a 2x2 optical star coupler 24 are provided on the light source 1 side, and the optical star coupler 24
, 5 μm band wavelength light and excitation light are combined, the combined light is transmitted via the optical fiber 2, and the optical fiber amplifier 13a is connected to the optical star coupler 12 on the optical tap 10 side.
After amplifying the wavelength light in the 1.5 μm band transmitted through the optical fiber 2, it is combined with the excitation light in the optical star coupler 12, and then this combined light is branched. In addition to obtaining the optical tap output, the next stage optical fiber 4
The reason is that it is configured to transmit light with a wavelength of 1.5 μm.

Even in such a configuration, the same effects as in the first embodiment can be obtained.

(Effects of the Invention) As explained above, according to claim (1), an excitation light source that emits excitation light, and a wavelength light in the 1.5 μm band transmitted through the excitation light and an optical fiber are combined. an optical star coupler that combines light, branches the combined light, and outputs the combined light; and a rare earth element-doped optical fiber amplifier that receives one branched light of the optical star coupler and amplifies the wavelength light in the 1.5 μm band. Further, in claim (2), an excitation light source that emits excitation light and a combined light of the excitation light and the wavelength light in the 1°5 μm band transmitted via the optical fiber are input. 1.
A rare earth element-doped optical fiber amplifier that amplifies wavelength light in the 5 μm band, and a wavelength light in the 1.5 μm band amplified by the rare earth element doped optical fiber amplifier and pump light from the pump light source are combined, and the combined light is Since the optical tap is configured with an optical star coupler that branches and emits the optical fiber, it is possible to compensate for optical loss due to the optical fiber and optical branching loss due to the optical star coupler with a simple configuration. This has the advantage of increasing your score.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a first embodiment of an optical fiber transmission system using an optical tap according to the present invention, Fig. 2 is a block diagram of a conventional optical fiber transmission system using an optical tap, and Fig. 3 FIG. 2 is a configuration diagram showing a second embodiment of an optical fiber transmission system using an optical tap according to the present invention. In the figure, 1... 1.5 μm band light source, 2, 4... Optical fiber for transmission line, 12.24... 2x2 optical star coupler, 11.23=--excitation light source, 1.3. 13 a-E
r (rare earth element) doped optical fiber amplifier, 21... optical filter, 22... light receiving element. Patent Applicant Nippon Telegraph and Telephone Corporation Agent Patent Attorney Yoshi 1) Takashi Sei 1]

Claims (2)

[Claims] (1) An excitation light source that emits excitation light, and a 1.5 μm optical fiber that transmits the excitation light and the optical fiber.
an optical star coupler that multiplexes wavelength light in the band, branches the combined light and outputs the combined light; and one branched light of the optical star coupler enters the optical star coupler, and
An optical tap comprising a rare earth element-doped optical fiber amplifier for amplifying m-band wavelength light. (2) A pumping light source that emits pumping light, and a rare earth element that inputs a combined light of the pumping light and the wavelength light in the 1.5 μm band transmitted through the optical fiber, and amplifies the wavelength light in the 1.5 μm band. an element-doped optical fiber amplifier; and 1 amplified by the rare-earth element-doped optical fiber amplifier.
．． An optical tap comprising an optical star coupler that combines wavelength light in the 5 μm band and excitation light from the excitation light source, branches the combined light, and emits the combined light.