JP2001111145A - Wide band ase light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wide band ASE light source which contains 1550 nm band and 1580 mn band, at a high output with a small excitation power. SOLUTION: A reflector 5 and an excitation light source 7 are multiplex- connected to one end of an amplifying optical fiber 3, and also an output terminal and another excitation light source 6 are multiplex-connected to another end, to constitute a wide band ASE light source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ASE light source for supplying excitation light to an amplification optical fiber and extracting ASE light.

[0002]

2. Description of the Related Art When an excitation light is input to an amplification optical fiber, the energy level of a rare earth material added therein rises, and when it returns to a stable state, light in the amplification signal band of the amplification optical fiber is emitted. You. The emitted light is called ASE (Amplified Spontaneous Emission) light. The ASE light source uses this ASE light as a light source, and is used for measuring the wavelength loss characteristics of an optical component in combination with a measuring instrument such as an optical spectrum analyzer.

FIG. 10 shows a first conventional example. Excitation light source 2
0 and an amplification optical fiber (EDF) 21 and an optical isolator 22 for preventing the excitation state of the amplification optical fiber from becoming unstable due to the return light from the output terminal. EDF by the excitation light output from the excitation light source 20
When the erbium in 21 is excited and its energy level rises and returns to a stable state (low energy level), ASE light is generated by energy release.

The band of the generated ASE light is usually 1530 to
1570 nm (1550 nm band), and when the EDF 21 is made 4 to 6 times the normal length, 1570 nm to 1610
nm (1580 nm band) (Reference 1: Ono et al.,
“Amplification Characteristics of 1.58 μm Band Er ³⁺ -doped Optical Fiber Amplifier” IEICE Technical Report, OCS97-5, pp25-29, 19
97). The full width at half maximum of ASE light is 3
6 nm (1567-1604 nm) and 40 nm (1563-1603 nm) of fluoride EDF have been achieved.

FIG. 11 shows an ED in the configuration of the first conventional example.
The ASE output is simulated by changing the length of F21. The excitation power is 100 mW, the EDF length is 20 to 150 m, and the simulation is performed at an excitation wavelength of 1480 nm because the excitation efficiency of 1480 nm is higher than that of 980 nm. 8, the ASE light wavelength band is changed from the 1550 nm band to 158
Although it shifts to the 0 nm band, it is understood that the ASE light power decreases when the EDF 21 is made too long.

As a second embodiment, although not shown, it is known that wideband (1530 to 1610 nm or more) signal amplification characteristics can be obtained by replacing the EDF with a tellurite-based EDF (not shown). Reference 2: Makoto
YAMADA et al., "Low-noise and gain-flattened Er ³⁺ d
oped tellurite fiber amplifier ", OAA'98 Technical
Digest, pp86-89,1998). According to this, a broadband AS
E-light can be obtained, but tellurite-based EDF is made of tellurite-based glass fiber with rare earth erbium added. It is less reliable than ordinary quartz-based EDF, and is specially hermetically sealed. Since it must be used in a package, it is not used in general optical communication systems.

[0007]

In order to increase the communication capacity, the wavelength band used for optical communication is being expanded. In addition to the 1530-1570 nm band used so far,
The 70 to 1610 nm band has also been used.
With the expansion of this wavelength band, optical communication components
An operation at 530 to 1570 nm or more is required, and a broadband ASE light source covering this wavelength band is required to measure the wavelength loss characteristics.

However, the quartz EDF and the fluoride E
In the first prior art using the DF, the ASE light output band is either 1530 to 1570 nm (1550 nm band) or 1570 nm to 1610 nm (1580 nm band), and one EDF has both bands.
SE light sources have not been developed.

Note that the above 1550 nm band and 1580 nm
Although it is possible to prepare two ASE light sources in a band and combine their outputs, there is a disadvantage that two light sources are required.

It is also conceivable to widen the band by using a tellurite-based EDF as the second conventional example, but it is not practical because it is very expensive and the handling is not easy. Further, the output power in the 1580 nm band is 1 in the 1550 nm band.
It is 1/0 or less, and a large pump power is required to increase the output power in the 1580 nm band.

Therefore, the present invention solves these problems by providing a high output, a 1550 nm band and a 1
It is an object of the present invention to provide an inexpensive broadband ASE light source including a 580 nm band.

[0012]

In order to solve the above-mentioned problems, the present invention combines a reflection or circulating means and an excitation light source at one end of an optical fiber for optical amplification, and an output terminal at the other end. It is characterized in that a single broadband ASE light source is formed by multiplexing and connecting one excitation light source.

The pump light is supplied from the two pump light sources to the amplification optical fiber, and ASE light having first and second wavelength bands is output from an output terminal.

The above-mentioned reflecting or circulating means is ASE
A means that reflects or circulates light back to its original direction.

[0015]

FIG. 1 shows a first embodiment of the present invention.

Amplifying optical fiber (hereinafter referred to as EDF)
One end of 3 is connected to a reflector 5 as an example of a reflection or circulation means via a multiplexer 4 and an excitation light source 7, and the other end is connected to another excitation light source 6 via a multiplexer 2. An optical isolator 1 is connected, and an output terminal for outputting ASE light through the optical isolator 1 is provided.

The pumping light output from the pumping light source 6 is guided to the EDF 3 via the multiplexer 2. The EDF 3 is an optical fiber having a light amplification function to which erbium as a rare earth element is added, and has a length of 50 to 140 m.

That is, in the conventional ASE light source, the EDF length is 10 m to 20 m and only the ASE light in the 1550 nm band is output.
By setting 7 times, ASE light output in the 1580 nm band is enabled.

When the pumping light from the pumping light source 6 enters, the first half of the EDF 3 on the multiplexer 2 side first has a wavelength of 1550 nm.
The ASE light of the band is emitted and propagates through the EDF3. The ASE light propagated to the optical isolator 1 is output from the optical isolator 1. The ASE light at 1550 nm is ED
The light also propagates to the reflector 5 side in F3 and is attenuated by being absorbed in the latter half of the EDF 3 in the middle. But 158
The ASE light in the 0 nm band propagates while being gradually amplified. Therefore, in order to output the ASE light in the 1580 nm band, the length of the EDF 3 must be 50 m to 140 m.
It is good if it is set as m.

The emitted ASE light in the 1580 nm band is reflected by the reflector 5, returned to the EDF 3, amplified in the EDF 3, and output through the optical isolator 1. However, in this state, 1 is output from the optical isolator 1.
The ASE light in the 580 nm band is about several percent of that in the 1550 nm band.

Therefore, in the present invention, the other excitation light source 7
Therefore, the excitation light is incident on the EDF 3. The pumping light output from the pumping light source 7 is guided to the EDF 3 to amplify the 1580 nm band ASE light generated by the pumping light source 6 and further amplifies the 1580 nm band ASE light and outputs the light from the optical isolator 1. Since the ASE light in the 1580 nm band at this time is sufficiently amplified, the ASE light in the 1550 nm band and the ASE light in the 1580 nm band are output in a relatively flat and combined state.

At this time, the power of the excitation light source 7 is
20% or less, and preferably about 10% or less of the power of the above.

FIG. 2 shows a second embodiment of the present invention, in which a single excitation light source 6 is provided, its output is distributed by a splitter 8, and excitation light is supplied from both sides of the EDF 3. You can also. In this case, the operation is similar to that of the first embodiment shown in FIG. According to this embodiment, since only one pump light source is required, the size and cost can be reduced. By adjusting the branching ratio of the branching device 8, the pump light supplied from both sides of the EDF 3 can be reduced. Power ratio can be adjusted freely.

FIG. 3 shows a third embodiment.

This embodiment uses a filter module in which the multiplexer 4 and the reflector 5 in the latter half of the ASE light source shown in FIG. 1 are integrated, and only the latter half of the ASE light source is shown. The filter type reflector 9 and the excitation light source 7 are connected to the side opposite to the output end of the EDF 3, and the filter type reflector 9 has a function of a filter and a reflector that reflects ASE light but transmits excitation light. Things.

Therefore, the ASE light generated by the EDF 3 is reflected by the filter-type reflector 9, while the excitation light of the excitation light source 7 can pass through the filter-type reflector 9 and enter the EDF 3. In this embodiment, it is possible to reduce the number of components by integrally configuring the multiplexer 4 and the reflector 5 in FIG.

In the above embodiment, the reflector 5 for reflecting the ASE light is used as the reflecting or circulating means. However, a circulating means for circulating and returning the ASE light may be used.

That is, in the fourth embodiment, as shown in FIG. 4, a fiber coupler 10 and a loop-shaped fiber 11 connected to the fiber coupler 10 are used as circulating means 12 instead of the reflector 5.
Can also be used.

The fiber coupler 10 is a 3 dB coupler having a branch ratio of about 1: 1. The loop-shaped fiber 11 has both ends of the optical fiber connected to the opposite side of the optical fiber coupler 10 from the EDF 3.

In this case, the ASE reaching the circulation means 12
The light splits at the fiber coupler 10 and is transmitted through the respective loop-shaped fibers 11 to be transmitted again to the fiber coupler 1.
The signals are multiplexed at 0 and transmitted in the opposite direction. At this time, since the optical path lengths of the loop fibers 11 are equal, the clockwise and counterclockwise lights in the loop fiber 11 undergo the same phase transition, and again enter the fiber coupler 10 having a branching ratio of 1: 1. When the phase of the combined light is reversed, the light is totally reflected to the in-phase side. That is, it has the same effect as when the total reflection mirror is used.

When the circulating means 12 is manufactured, the fiber coupler 10 is connected to the end of the multiplexer 4 and both ends of the optical fiber are fusion-spliced to the other end to form the loop fiber 11, Alternatively, the optical fiber provided at the end of the multiplexer 4 may be formed into a loop shape, and the end may be fused and drawn to the original optical fiber to produce the fiber coupler 10.

If such a circulating means 12 is used, it can be manufactured at a lower cost than the reflector 5 of the total reflection mirror.

In any of the above embodiments, the ED
Even if a quartz optical fiber or a fluoride optical fiber is used as F3, a sufficient output can be obtained, and an ASE light source can be easily manufactured.

Further, in the above embodiment, the multiplexers 2 and 4 are formed by fusing and stretching two single mode fibers, which are joined to the EDF 3.
Fiber couplers forming the multiplexers 2 and 4 can be formed in the DF 3 itself. For example, if the multiplexers 2 and 4 are formed at the ends of the EDF 3 itself by fusing and stretching the EDF 3 and a single mode fiber having a propagation constant substantially equal to the EDF 3, the number of connection portions can be reduced and the loss can be reduced. it can.

As shown in FIG.
3 is a single mode fiber 1 for propagating pump light
3 is fusion spliced, and 10 to 15 m from the fusion spliced portion 14.
The multiplexer 4 can be formed by fusing and stretching the EDF 13 portion of about m with a single mode fiber 15 having a propagation constant substantially equal to this.

In this case, the pump light is multiplexed near both ends of the EDF 3, and the single mode fiber 13
Is also integrally formed in the case of the multiplexer 4.

In the case of the embodiment shown in FIG. 4, the fiber coupler 10 can be formed by the EDF 3 itself.

[0038]

FIG. 6 shows a simulation of the ASE light output of the ASE light source of the first embodiment shown in FIG.

The excitation light source 6 (LD6) and the excitation light source 7 (L
D7) are both 980 nm wavelength and each output is 100 m
W, 0 mW to 20 mW, and EDF3 is a commercially available silica-based erbium-doped optical fiber having a length of 50 mW.
１５０150 m. The reflectance of the reflector 5 is 90%, and does not include the loss of the optical isolator 1, the multiplexers 2, 4, and the like.

Since it is desirable that the output of the spectrum of the ASE light for measurement is large and flat, FIG.
From the results of, LD6 = 100 mW, LD7 = 10 mW,
It can be said that an EDF length of about 100 m is appropriate. In addition,
If the pump power (power of LD6, LD7) is increased, A
Although the SE power also increases, an unnecessary increase is not preferable because the excitation light source is expensive.

FIG. 7 shows a simulation obtained by changing the wavelength of the excitation light source to 1480 nm in the above configuration. As a result, when the quartz EDF is made longer, AS
It can be seen that the E light wavelength band shifts from the 1550 nm band to the 1580 nm band, and it is difficult to configure a broadband ASE light source that satisfies the 1550 nm band and the 1580 nm band. Therefore, the wavelength of the excitation light source is preferably in the 980 nm band.

FIG. 8 shows an excitation wavelength of 980 nm and LD6 = 90.
mW, LD7 = 12 mW, EDF length (quartz EDF) =
Simulation result at 90 m, 1530 nm
Optical power density -13 dBm / n in the range of ~ 1600 nm
A light source with a bandwidth of at least m is obtained.

In the example shown in FIG.
FIG. 9 shows the result of actually producing the light source and measuring the output, which almost coincided with the simulation result of FIG.

[0044]

According to the present invention, a reflection or circulation means and an excitation light source are multiplexed and connected to one end of an amplification optical fiber, and an output terminal and another excitation light source are multiplexed and connected to the other end. By constructing a broadband ASE light source, quartz-based or fluoride-based E
Even if DF is used, it is possible to use a low excitation power of 1530 nm to 16
It is possible to obtain high-output ASE light in a wide band of 10 nm or more.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a broadband ASE light source of the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the broadband ASE light source of the present invention.

FIG. 3 is a configuration diagram showing another embodiment of the broadband ASE light source of the present invention.

FIG. 4 is a configuration diagram showing another embodiment of the broadband ASE light source of the present invention.

FIG. 5 is a configuration diagram showing another embodiment of the broadband ASE light source of the present invention.

FIG. 6 is a diagram simulating the output of a broadband ASE light source according to the present invention.

FIG. 7 is a diagram simulating the output of a broadband ASE light source according to the present invention.

FIG. 8 is a diagram simulating the output of a broadband ASE light source according to the present invention.

FIG. 9 is an actual measurement diagram of a spectrum waveform by the broadband ASE light source according to the present invention.

FIG. 10 is a configuration diagram showing a conventional ASE light source.

FIG. 11 is a diagram simulating the output of a conventional ASE light source while changing the EDF length.

[Explanation of symbols]

 1: optical isolator 2: multiplexer 3: optical fiber for optical amplification (EDF) 4: multiplexer 5: reflector 6: excitation light source 7: excitation light source 8: duplexer 9: filter type reflector 10: fiber coupler 11: Loop fiber 12: Circulation means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Michitaka Okuda 2-1-1 Kagahara, Tsuzuki-ku, Yokohama-shi, Kanagawa Prefecture F-term in Kyocera Corporation Yokohama Office 5F072 AB09 AK06 JJ04 JJ20 KK05 KK30 RR01 YY17

Claims (9)

[Claims] 1. A broadband ASE light source wherein a reflection or circulation means and an excitation light source are multiplexed and connected to one end of an optical amplification optical fiber, and an output terminal and another excitation light source are multiplexed and connected to the other end. . 2. The apparatus according to claim 1, wherein said two pumping light sources supply pumping light to an optical amplification optical fiber, respectively, and output ASE light having first and second wavelength bands from an output terminal. Item 2. A broadband ASE light source according to item 1. 3. The first and second wavelength bands are 1530-1570 nm (1550 nm band) and 157 nm, respectively.
3. The broadband ASE light source according to claim 2, wherein the output light includes 0 to 1610 nm (1580 nm band), and the combined output light includes a 1530 to 1610 nm band. 4. A wavelength of said excitation light is in a 980 nm band.
3. The broadband ASE light source according to claim 2, wherein the ratio of the excitation light supplied from the reflection or circulation means side to the excitation light supplied from the output terminal side to the optical amplification fiber is 20% or less. . 5. The broadband ASE according to claim 1, wherein the optical fiber for optical amplification is a silica-based optical fiber or a fluoride-based optical fiber doped with erbium, and has a length of 50 m or more. light source. 6. The broadband AS according to claim 1, wherein the output of one pumping light source is branched via an optical branching means and multiplexed and connected to one end and the other end of the amplification optical fiber.
E light source. 7. The broadband AS according to claim 1, wherein the reflection or circulation means provided at one end of the optical amplification optical fiber comprises a filter that reflects an ASE light component.
E light source. 8. The broadband ASE light source according to claim 1, wherein the reflection or circulation means provided at one end of the optical fiber for optical amplification comprises a fiber coupler and a loop-shaped fiber connected to the fiber coupler. 9. The broadband ASE light source according to claim 1, wherein a fiber coupler for multiplexing the pump light is formed near both ends of the optical amplification optical fiber itself.