JPH04306624A - Selecting method of light wave length of wave length selecting element - Google Patents

Abstract

PURPOSE:To vary the wave length of the light selected by an optical fiber by inputting control light to an optical fiber on which rare-earth metals are doped to conduct ON/OFF-operation. CONSTITUTION:Control light for controlling the characteristic of an optical fiber 1 is inputted from a control light source 5 to an optical fiber 1 (wave length selecting element) on which rare-earth metals are doped, and the control light is ON/OFF-operated. Accordingly, the light transmission and damping characteristic of the rare-earth metals in the optical fiber 1 change, and the light wave length selected by the optical fiber 1 can be varied. Further, when the wave length of the control light is set to the vicinity of the light absorption wave length band which is common to a plurality of rare-earth metals for the doping on the optical fiber 1, the light transmission and damping characteristic of a plurality of rare-earth metals in the optical fiber 1 can be varied by a single control light source 5, and the control light source 5 can be effectively utilized.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention changes the transmission and attenuation characteristics of the rare earth element doped in the wavelength selection element by controlling light inputted from the outside into the optical fiber (wavelength selection element). The present invention relates to an optical wavelength selection method using a wavelength selection element that allows the selected optical wavelength to be changed.

0002

2. Description of the Related Art Conventionally, there have been the following wavelength selection elements. (1) A multilayer dielectric film laminated on a glass substrate, etc. In this wavelength selection element, the wavelength selection characteristics are determined by the thickness and number of multilayer films. Further, the characteristics change slightly when the angle with respect to the incident light is changed. (2) A combination of parts of two optical waveguides. WDM
This type of optical fiber coupler falls under this category. In this wavelength selection element, wavelength selection characteristics are determined by the length of the bond. (3) Optical fiber doped with dopants such as rare earth elements. This wavelength selection element utilizes an absorption line specific to the dopant, and attenuates incident light having a wavelength that matches the absorption line, while transmitting wavelengths that do not match the absorption line.

0003

[Problem to be solved by the invention] Conventional methods (1) to (1)
Once manufactured, the transmission and attenuation characteristics of the wavelength selection elements 3) cannot be easily changed, so it is difficult to change the selected wavelength by external control. Furthermore, the method (1) of changing the transmission and attenuation characteristics by changing the angle has the disadvantage that the wavelength selection range is narrow.

0004

[Object of the invention] The purpose of the present invention is to change the transmission and attenuation characteristics of rare earth elements in the wavelength selection element by using an optical fiber as a wavelength selection element and turning on/off the control light input to the wavelength selection element. Another object of the present invention is to provide a wavelength selection method that allows changing the wavelength selected by a wavelength selection element.

[0005]

[Means for Solving the Problems] The wavelength selection method of the wavelength selection element of the present invention, as set forth in claim 1, is directed to an optical fiber 1 doped with at least one kind of rare earth element (wavelength A control light that controls the characteristics of the wavelength selection element 1 is inputted from the control light source 2 into the selection element 2, and by turning the control light on and off, the light transmission and attenuation characteristics of the rare earth in the wavelength selection element 1 are controlled. The optical wavelength selected by the wavelength selection element 1 is changed by changing the wavelength selection element 1. Among the wavelength selection methods of the wavelength selection element of the present invention, the method according to claim 2 includes setting the wavelength of the control light near a light absorption wavelength band common to a plurality of rare earth elements doped in the wavelength selection element 1. Accordingly, the light transmission and attenuation characteristics of a plurality of rare earth elements in the wavelength selection element 1 can be changed using a single controlled light source 2. According to a third aspect of the wavelength selection method of the wavelength selection element of the present invention, the wavelength selection element 1 is an optical fiber doped with erbium (Er) and neodymium (Nd), and the wavelength of the control light is 0.7
It is characterized by being between 5 μm and 0.85 μm.

[0006]

[Operation] FIG. 2 shows the energy level of erbium ions doped into a silica-based optical fiber. In the absence of control light, most of the erbium ions in the fiber are in their ground state (4I15/2). Therefore, as shown in Figure 3, the wavelengths corresponding to electronic transition from the ground state are 0.66 μm, 0.8 μm, 0.98 μm,
An absorption peak exists near 1.54 μm. This absorption is called GSA (ground state absorption).
on) is called. When control light matched to the wavelength of GSA is incident here, the erbium ions absorb the light, and a portion or most of the erbium ions come to exist in an excited state (4I13/2). In the state where the control light is incident, as shown in Figure 4, the wavelengths corresponding to electron transition from the excited state are 0.64 μm, 0.71 μm, 0.79 μm, and 0.8 μm.
An absorption peak appears around 5 μm. This absorption is ESA
(excited state absorption)
It is called. On the other hand, absorption by GSA becomes smaller. Such properties can be utilized in switches that are selective to optical wavelengths. For example, focusing on two wavelengths of 0.71 μm and 0.98 μm, their transmission and attenuation characteristics are as follows. In this way, the wavelength selection characteristics of the wavelength selection element can be changed by turning on/off the control light. Such characteristics are also seen in optical fibers doped with other rare earth elements (Nd, Sm, Tm, etc.). For example, in neodymium (Nd) doped optical fibers, 0.59 μm, 0.68 μm,
GSA around 0.74μm, 0.8μm, 0.88μm
ESA exists near 1.3 μm. Therefore, by doping one optical fiber with two or more types of rare earths or by connecting optical fibers doped with different rare earths, it is possible to produce various wavelength selection elements with different characteristics. In particular, doped rare earths can cause GSA to a common wavelength.
This is advantageous because the absorption characteristics of a plurality of rare earths can be changed simultaneously by turning on/off a single controlled light source set to that wavelength. For example, both erbium (Er) and neodymium (Nd) have a thickness of 0.8 μm.
Since we have a GSA nearby, we can control it with a single light source. Also, for Er, GSA is in the 1.55 μm band, and for Nd, it is in the 1.55 μm band.
It has ESA in the 3 μm band. Since these wavelengths are often used in optical fiber communications, the combination of Er and Nd is also effective in that sense.

[0007]

[Embodiment] FIG. 1 shows an embodiment of the optical wavelength selection method of the wavelength selection element of the present invention. In Figure 1, 1 is an optical fiber doped with both Er and Nd (wavelength selection element), 3 is 1.2
It is an optical filter that transmits light with a wavelength of .mu.m or more and reflects light with a wavelength of 0.9 .mu.m or less. This optical filter 3 is coupled to the optical fiber 1 via an optical fiber 4. 5 is a 0.8 μm semiconductor laser (LD) serving as a control light source. This semiconductor laser 5 is coupled to an optical filter 3 via an optical fiber 6. 7 and 8 in FIG. 1 are input/output terminals. 1.3 μm from the input end 7 to the wavelength selection element 1
Considering that light in the band or 1.55 μm band is incident, the operation of the device shown in FIG. 1 is as follows. (a) When LD5 is not lit. The 1.3 μm band light incident from the input end 7 passes through the wavelength selection element 1,
The light is emitted from the input end 8. 1. Incoming from the input end 7.
The light in the 55 μm band is the ES of Er ions in the wavelength selection element 1.
The light is absorbed by A and is emitted from the output end 8 in an attenuated state. (b) When LD5 is lit. Light in the 1.3 μm band incident from the input end 7 is absorbed by the ESA of Nd ions in the wavelength selection element 1, and is emitted from the output end 8 in an attenuated state. Light in the 1.55 μm band incident from the input end 7 is transmitted through the fiber 1 or amplified by stimulated emission of Er in the wavelength selection element 1, and then sent to the output end 8.
It is emitted from. This function can be summarized as follows: 1.3μm
1.55μm LD on transmission
Attenuation LD off Attenuation
Transmission or amplification thus LD5
The transmission/attenuation characteristics in the 1.3 μm/1.55 μm band are reversed by turning on/off the . Input end 7 to output side, output end 8
It works in the same way when used as an input side. In this case, it is effective to connect an optical filter to the input end 7 for cutting the control light transmitted through the wavelength selection element 1.

[0008]

Effects of the Invention The optical wavelength selection method of the wavelength selection element of the present invention has the following effects. ■． By simply turning on/off the control light incident on the wavelength selection element 1 doped with rare earth elements, you can
By changing the attenuation characteristics, the selected wavelength can be changed. ■． By setting the wavelength of the control light near the light absorption wavelength band common to the rare earths to be doped, it is possible to change the light transmission and attenuation characteristics of multiple rare earths with a single control light, making it possible to improve the control light source. will be used effectively. ■． The dopants in the optical fiber are erbium and neodymium, and the wavelength of the control light is 0.75 μm to 0.85 μm.
By setting the wavelength between the 1.55 μm band and the 1.3 μm band, which are often used in optical fiber communication, it is possible to select a wavelength between the 1.55 μm band and the 1.3 μm band, which are often used in optical fiber communication. ■． It has the advantage that it is independent of the polarization state of incident light and that the extinction ratio during on/off can be freely set by changing the fiber length and dopant concentration.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the optical wavelength selection method of the wavelength selection element of the present invention.

FIG. 2 is an energy level diagram of erbium ions doped into a silica-based optical fiber.

FIG. 3 is an explanatory diagram showing a GSA spectrum of erbium ions.

FIG. 4 is an explanatory diagram showing an ESA spectrum of erbium ions.

[Explanation of symbols]

1 Wavelength selection element 2 Control light source

Claims (3)

[Claims] Claim 1: A control light source 2 is connected to an optical fiber 1 (wavelength selection element) doped with at least one kind of rare earth element.
A control light for controlling the characteristics of the wavelength selection element 1 is inputted from the wavelength selection element 1, and by turning the control light on and off, the light transmission and attenuation characteristics of the rare earth in the wavelength selection element 1 are changed.
An optical wavelength selection method for a wavelength selection element, characterized in that the optical wavelength selected by the wavelength selection element 1 is changed. 2. In claim 1, the wavelength of the control light is
By setting near the light absorption wavelength band common to the plurality of rare earth elements doped in the wavelength selection element 1, the light transmission and attenuation characteristics of the plurality of rare earth elements in the wavelength selection element 1 can be changed with a single control light source 2. A method for selecting an optical wavelength using a wavelength selection element, characterized in that: 3. The wavelength selection element 1 according to claim 1 comprises:
The optical fiber 1 is doped with erbium (Er) and neodymium (Nd), and the wavelength of the control light is 0.75 μm.
and 0.85 μm.