JPH04234736A - Fiber type optical amplifier - Google Patents

Abstract

PURPOSE:To stabilize the level of excitation light by providing two pieces of light sources for excitation and automatically switching the light sources when one thereof is deteriorated or goes out of order. CONSTITUTION:Two or more pieces of the light sources 2, 5 for excitation are provided. These light sources are automatically switched by a switching part 6 to the other light sources 2, 5 for which are not used when the level of the exciting light outputted from the one light sources 2, 5 for excitation falls to a prescribed value or below. The exciting light is then outputted from the fresh light sources 2, 5 for excitation. The level of the exciting light transmitted to an optical fiber 1 is stabilized and the interruption of the transmission of the exciting light to the optical fiber 1 is obviate even if the one light sources 2, 5 for excitation do not operate normally any more.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber type optical amplification device using an optical fiber doped with rare earth element ions which exhibits an optical amplification effect upon optical excitation.

0002

[Prior Art] In recent years, Er has been added to the core of silica-based optical fibers.
Research is actively being carried out on optical fibers that incorporate rare earth element ions such as Nd and Nd and utilize the optical amplification effect of these ions upon optical excitation. For example, a quartz-based single molten resin containing several tens to 100 ppm of Er ions is used.
In a doped optical fiber (Er-doped fiber), a wavelength of 1450 nm generated from an excitation light source (for example, a semiconductor laser)
When pumping light of m to 1540 nm is input through an optical multiplexer, signal light of 1530 nm to 1650 nm can be amplified.

In the case of Er-doped fibers, a pumping light wavelength of around 980 nm is also promising. Furthermore, the optical amplification effect can also be achieved with fibers mixed with rare earth elements or transition metals other than Er.

[0004] This optical fiber can be combined with other optical members to form a fiber-type optical amplification device as shown in FIG. In the fiber type optical amplifier shown in FIG. 2, pumping light sent out from a pumping light source 11 such as a semiconductor laser and signal light input from an input terminal 12 to an optical fiber 13 are combined by an optical fiber coupler 14. The signal light is guided to an optical fiber 15 doped with rare earth element ions, and the rare earth element ions are optically excited by the excitation light to amplify the signal light.

In FIG. 3, 16 is an optical isolator, and 17 is an optical isolator.
is the output terminal. Further, the optical isolator 16 and the optical fiber 15 in FIG. 3 are fusion spliced or connected with a connector at a connection point O.

[0006]

However, the light source for excitation light may deteriorate over time, resulting in a decrease in the output of the excitation light, or may become damaged, causing no excitation light to be output at all. In such a case, the rare earth element ions within the optical fiber are insufficiently excited or are not excited at all, resulting in insufficient optical amplification in the optical fiber.

[0007]

[Object of the Invention] An object of the present invention is to realize a fiber-type optical amplification device that can obtain pumping light of a sufficient level to pump rare earth elements even if the pumping light source stops operating normally. It is in.

[0008]

[Means for Solving the Problems] As shown in FIG. 1, the fiber type optical amplification device of the present invention pumps excitation light for exciting rare earth element ions into an optical fiber 1 doped with rare earth element ions. The signal light a transmitted from the optical light source 2 and supplied to the optical fiber 1 is amplified, a part of the output light b from the optical fiber 1 is taken out, and its level is monitored by the monitoring light detector 3. , depending on the monitoring results, the excitation light source 2
A fiber-type optical amplification device in which a drive current supplied to the optical fiber 1 is controlled by a control unit 4 to control the level of pumping light output from a pumping light source 2 and to stabilize the level of output light from an optical fiber 1. In this case, two or more excitation light sources are provided, and when the excitation light level output from any of the excitation light sources 2 or 5 becomes below a predetermined value, the excitation light source 2
or 5 to another excitation light source 5 or 2 by a switching unit 6.

[0009]

[Operation] In the fiber type optical amplifier of the present invention, when the level of the pumping light output from one of the pumping light sources 2 or 5 becomes below a predetermined value, the pumping light source 2 or 5 that is in use is not used. The switching unit 6 automatically switches to the excitation light source 5 or 2, and excitation light is output from the new excitation light source 5 or 2. Even if the optical fiber 1 ceases to operate normally due to deterioration or damage, the level of the excitation light transmitted to the optical fiber 1 does not decrease.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 showing an embodiment of the fiber type optical amplification device of the present invention, reference numeral 1 denotes an optical fiber having an optical amplification function. This optical fiber 1 has rare earth element ions such as Er and Nd mixed therein, for example, Er ions contain 530
A ppm doped single mode fiber is used.

Reference numerals 2 and 5 in FIG. 1 are excitation light sources, for example, semiconductor lasers having an oscillation wavelength of 1470 to 1480 nm are used. These two excitation light sources 2 and 5 are coupled by a multiplexer 21 such as a polarization coupler or a mechanical switch. The output side optical fiber 22 of this multiplexer 21 is coupled to the input side of the optical fiber 1 by an optical multiplexer 23 so that the excitation light generated from the excitation light source 2 or 5 is transmitted to the optical fiber 1. There is.

In FIG. 1, 25 is an isolator, and 26 is a filter. Reference numeral 27 in FIG. 1 is an optical demultiplexer, which connects the output side of the optical fiber 1 and the monitoring photodetector 3 to send a part of the output light b of the optical fiber 1 to the monitoring photodetector 3. This is for splitting into two.

The monitoring light detection section 3 is for detecting the level of the output light from the optical fiber 1, and uses, for example, a phato diode PD.

Reference numeral 4 in FIG. 1 is a control section, which controls the drive current supplied to the excitation light source 2 in accordance with the monitoring result in the monitoring light detection section 3, and outputs the excitation light source 2 from the excitation light source 2. The purpose of this is to control the level of the pumping light, thereby controlling the optical amplification in the optical fiber 1, and to stabilize the level of the optical signal b output from the optical fiber 1.

Reference numeral 6 in FIG. 1 is a switching unit, which switches the excitation light from one of the excitation light sources 2 that has been used until then when the level of the excitation light output from the excitation light source 2 becomes below a predetermined value. This is for switching to another excitation light source 5 that has not been used until now. In this case, the level detection of the excitation light is performed, for example, as follows. The drive current supplied from the control unit 4 to the excitation light source 2 is monitored, and when the drive current exceeds a predetermined value (a large amount of drive current is required), the excitation light output of the excitation light source 2 in use is It is determined that the capacity has decreased, and based on that determination, the switching unit 6 switches to another excitation light source 5 that has not been used up to that point. Note that the excitation light level is detected not by directly monitoring the drive current, but by measuring a resistance value that controls the drive current, and indirectly detecting the drive current from the resistance value. Other methods are also possible.

[0016]

[Effects of the Invention] The fiber type optical amplification device of the present invention has the following effects. ■． If the excitation light source 2 or 5 in use ceases to operate normally due to deterioration over time or failure, excitation light is automatically output from the other excitation light source 5 or 2 that has not been used up to that time. Even if the excitation light source 2 or 5 stops operating normally, the level of excitation light transmitted to the optical fiber 1 remains stable. ■． Even when a failed excitation light source is replaced with a new excitation light source, the transmission of the excitation light to the optical fiber 1 is not interrupted, so the communication being carried out by transmitting the signal light a to the optical fiber 1 is also not interrupted.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of a fiber type optical amplification device of the present invention.

FIG. 2 is an explanatory diagram showing an example of a conventional fiber-type optical amplification device.

[Explanation of symbols] 1 Optical fiber 2. Excitation light source 3. Monitoring light detection section 4 Control section 5. Excitation light source 6 Switching section

Claims (1)

[Claims] 1. A signal light a supplied to the optical fiber 1 by transmitting excitation light for exciting the rare earth element ions from an excitation light source 2 to the optical fiber 1 doped with rare earth element ions. A part of the output light b from the optical fiber 1 is amplified and its level is monitored by the monitoring light detection unit 3, and the control unit 4 controls the drive current to be supplied to the excitation light source 2 according to the monitoring result. In the fiber type optical amplifier device, the level of the pumping light output from the pumping light source 2 is controlled by the pumping light source 2, and the level of the output light from the optical fiber 1 is stabilized. When the level of excitation light output from any of the excitation light sources 2 or 5 falls below a predetermined value, the switching unit 6 automatically switches from that excitation light source 2 or 5 to the other excitation light source 5 or 2. A fiber type optical amplification device characterized by the following features.