KR20020053974A - Gain clamped erbium-doped fiber amplifier - Google Patents

Abstract

PURPOSE: A device for gain fixing optical amplification is provided to obtain a constant gain about an input signal which has a wide wavelength band by preparing a laser diode at an input tap and operating an optical feedback circuit at an output tap. CONSTITUTION: A control unit(310) offers a signal which is controlled to a constant intensity regardless of a channel number of an optical signal inputted from outside. An amplification unit(320) amplifies the signal which is controlled to the constant intensity in the control unit(310). A feedback unit(330) divides the signal amplified in the amplification unit(320) and offers the divided signal to the amplification unit(320) with the signal controlled to the constant intensity in the control unit(310).

Description

Gain clamped erbium-doped fiber amplifiers

The present invention relates to a gain-fixed optical amplifier, and more particularly, by providing a laser diode at an input terminal of the optical amplifier, and returning the output of the optical amplifier back to the input using an optical feedback circuit. The present invention relates to a gain fixed optical amplifier which can obtain a constant gain even for an input signal having a wide wavelength band.

1 is a diagram illustrating a configuration of a gain fixed optical amplifier using a conventional optical feedback circuit.

As shown in Fig. 1, a gain fixed optical amplifier using a conventional optical feedback circuit is well introduced in US Patent 6,094,298 (July 25, 2000) proposed by 'Gengxian Luo'.

The contents are as follows.

A part of the output signal of the optical amplifier is connected to the input terminal, and the variable attenuator 180 for controlling gain and the variable wavelength filter 160 for selecting an oscillation wavelength are connected together.

At the oscillation wavelength, the loss value of the laser resonator coincides with the gain, and since the gain medium EDF has homogeneity at room temperature, the gain is fixed to the loss value even in the wavelength band near the oscillation wavelength.

2 is an exemplary configuration diagram of a control circuit for fixing an input signal of a conventional gain fixed optical amplifier.

As shown in FIG. 2, a control circuit for fixing an input signal of a conventional optical amplifier is known as' Electronics Letters, vol. 9, pp. It is well introduced in 1667-1669.

The contents are as follows.

The laser diode 250 and the control circuit 240 are installed at the input terminal of the optical amplifier, so that a constant input is maintained in the optical amplifier regardless of the variation in the number of channels of the input optical signal.

Thus, the above method exhibits a characteristic that the output of the optical amplifier is naturally maintained by keeping the input intensity itself of the optical amplifier constant.

Here, the gain fixed optical amplifier using the optical feedback circuit proposed by 'Gengxian Luo' and the control circuit for fixing the input signal of the optical amplifier proposed by the 'AKSrivastava' are both gain medium EDF. It can be seen that using the homogeneity of.

That is, in the case of the above two devices, the control channel, the automatic gain control wavelength or the laser diode wavelength is slightly away from the wavelength actually amplified, but the gain medium has a high homogeneity at room temperature, so even if the control channel is slightly away from the control wavelength, Receive. However, when the wavelength band to be amplified is very wide and 20 nm or more, it is effective to control at two wavelengths far from each other than using one control channel.

However, in the fixed gain optical amplifier using the optical feedback circuit proposed by 'Gengxian Luo', the relaxation oscillation phenomenon occurs when the output reaches a steady state due to a change in the input. Therefore, there is a problem that an error may occur during transmission because the output is momentarily very large or small at the time when the input changes.

In addition, the control circuit for fixing the input signal of the optical amplification device proposed by the 'AKSrivastava', the intensity of the control laser diode is also increased when the change of the input is large, so that the output is also very large do.

In this case, spectral holes are generated in the control channel, and the gain spectrum in the signal wavelength band has a large change. Such a change has a problem in that a serious gain deviation can be caused when the wavelength band used is wide.

The present invention proposed to solve the problems described above, by providing a laser diode at the input terminal of the optical amplifier, and returning the output of the optical amplifier back to the input using the optical feedback circuit, a wide wavelength band It is an object of the present invention to provide a gain fixed optical amplifier which can obtain a constant gain even with respect to an input signal.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram illustrating a configuration of a gain fixed optical amplifier using a conventional optical feedback circuit.

2 is an exemplary configuration diagram of a control circuit for fixing an input signal of a conventional gain fixed optical amplifier.

3 is a block diagram of an embodiment of a fixed gain optical amplifier using the control circuit and the optical feedback circuit according to the present invention.

* Explanation of symbols for the main parts of the drawings

310: control unit 320: amplification unit

330: feedback

The present invention for achieving the above object is a gain fixed optical amplification apparatus for obtaining a constant gain even for an input signal having a wide wavelength band, a constant intensity irrespective of the number of channels of the optical signal received from the outside Signal control means for providing a controlled signal; Signal amplifying means for receiving and amplifying a signal controlled by the signal control means with a constant intensity; And signal feedback means for branching a part of the signal amplified by the signal amplifying means and providing it as an input signal of the signal amplifying means like a signal controlled by the signal control means at a constant intensity. It is done.

In addition, the present invention is a gain fixed optical amplifier for obtaining a constant gain even for an input signal having a wide wavelength band, the part of the signal amplified by the gain fixed optical amplifier, branching the gain Signal feedback means for providing as an input signal of the fixed optical amplifier; Signal control means for providing a controlled signal at a constant intensity irrespective of the number of channels of the optical signal received by the signal feedback means; And signal amplifying means for receiving and amplifying a signal controlled by the signal control means with a constant intensity.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram of an embodiment of a fixed gain optical amplifier using a control circuit and an optical feedback circuit according to the present invention.

As shown in FIG. 3, the fixed gain optical amplification apparatus using the control circuit and the optical feedback circuit according to the present invention is for providing a controlled signal with a constant intensity regardless of the number of channels of an optical signal input from the outside. The control unit 310, the amplifying unit 320 for receiving and amplifying a signal controlled by a certain intensity by the control unit 310 and a part of the signal amplified by the amplifying unit 320, branching the control ( Like a signal controlled to a certain intensity by the unit 310, it includes a feedback unit 330 for providing as an input signal of the amplifier 320.

Here, the amplifier 320, the laser diodes (322, 326, 329) for generating a pumping light source for amplification, advertisers (321, 324, 328) for advancing the signal in one direction only, using the pump light generated by the laser diodes (322, 326, 329) A general two-stage amplified erbium-doped optical fiber amplifier is provided with EDFs 323 and 327 for amplifying signals and a gain flattening filter 324 for filtering one-stage amplified optical signals.

In addition, the control unit 310 receives an optical signal from an external optical splitter 311 for distributing an optical signal and an optical signal distributed from the optical splitter 31 and receives an electrical signal proportional to its intensity. A photodetector 313 for generating an electronic control circuit, an electronic control circuit 315 for generating an electronic control signal linearly inversely proportional to an electrical signal detected by the photodetector 313, and generated by the electronic control circuit 315. A laser diode 314 for generating a laser pump light for gain control according to an electronic control signal and a laser pump light generated by the laser diode 314 and an optical signal from the other side distributed by the optical splitter 311 are combined and output. Wavelength selective coupler 312.

The feedback unit 330 variably attenuates the amplified optical signal received from the optical splitter 333 and the optical splitter 333 for receiving and distributing the optical signal amplified by the amplifier 320. Wavelength for receiving the variable optical attenuator 332 and the optical signal attenuated by the variable optical attenuator 332 and combined with the output optical signal of the control unit 310 to provide as an input signal of the amplifier 320 A select coupler 331.

Looking at the detailed function and operation of each component as follows.

When the input signal is input to the input terminal of the optical splitter 311, some of it is branched to the photodetector 313 and the other part is to the input terminal of the wavelength selective combiner 312. In the photodetector 313, a current proportional to the detected light intensity enters the electronic control circuit 315, and a current is applied to the laser diode 314 in a linear inverse proportion to this intensity.

That is, if the number of input channels is large and the detected current is large, a small current is applied to the laser diode 314. If the number of input channels is small, a large current is applied.

The output of the laser diode 314 operating in this manner enters the input of the wavelength selective combiner 312 and is coupled to the signal to be transmitted to the output.

In this case, the wavelength of the laser diode 314 is to have a wavelength near the shortest signal wavelength, and the wavelength selective coupler 312 must also have a characteristic capable of simultaneously combining the signal wavelength and the wavelength of the control laser diode.

The signal coupled from the wavelength selective combiner 312 is connected to an input terminal of the wavelength selective combiner 331 of the feedback unit 330 and input to the amplifier 320.

The first adsorber 321, the first laser diode 322, the second adsorber 325, and the second laser diode 326 of the amplifying unit 320 are pumped in the same direction in which the signal travels. The output pump signal of the laser diode is input, and the third adsorber 328 and the third laser diode 329 input the output pump signal of the pumping laser diode in the opposite direction in which the signal proceeds.

The signal input to the amplifier 320 is coupled to the output of the first laser diode 322 while passing through the first advertiser 321 and input to the first EDF 323 to be amplified by one stage. As a result of the one-stage amplification process, the degree of amplification may be different according to the signal wavelength. Therefore, the signal amplified largely through the gain flattening filter 324 and the signal amplified smaller than this are attenuated to different degrees.

The output of the gain flattening filter 324 is coupled to the output of the second laser diode 326 at the second granulator 325 and input to the second EDF 327 for amplification once again.

In the process of two-stage amplification by the second EDF 327, a third granulator 328 and a third laser diode 329 for reverse pumping are added to increase the amplification rate.

The two-stage amplified signal through the above process, through the optical splitter 333, a part is finally output, the other part is used as an input signal of the feedback unit 330 is connected to the variable optical attenuator 332.

The output of the variable optical attenuator 332 is connected to the wavelength selective combiner 331 again, thereby forming a feedback circuit in which a part of the amplified signal enters the input unit again.

In this case, the feedback circuit constituting the feedback unit 330 has a form similar to a ring laser, and the wavelength of oscillation is determined according to the selected wavelength of the wavelength selective coupler. The wavelength oscillated by the optical feedback circuit should be near the longest signal wavelength, and should be 20 nm or more away from the wavelength of the control channel input to the controller 310.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains, and the above-described embodiments and accompanying It is not limited to the drawing.

As described above, the present invention can obtain a constant gain even for an input signal having a wide wavelength band, and thus, there is an effect that an economic and efficient gain fixed optical amplifier can be realized.

Claims (7)

A gain fixed optical amplifier for obtaining a constant gain even for an input signal having a wide wavelength band, Signal control means for providing a controlled signal with a constant intensity irrespective of the number of channels of the optical signal received from the outside; Signal amplifying means for receiving and amplifying a signal controlled by the signal control means with a constant intensity; And Signal feedback means for branching a part of the signal amplified by the signal amplifying means and providing it as an input signal of the signal amplifying means, such as a signal controlled by the signal control means at a constant intensity Gain fixed optical amplifier device comprising a. The method of claim 1, The signal control means, Optical distribution means for receiving and distributing optical signals from the outside; Signal detection means for receiving an optical signal of one side distributed by the light distribution means and generating an electrical signal proportional to the intensity; Electronic control means for generating an electronic control signal linearly inversely proportional to the electrical signal detected by said signal detecting means; Signal pumping means for generating a gain control laser pump light in accordance with an electronic control signal generated by said electronic control means; And Wavelength selective coupling means for combining and outputting the laser pump light generated by the signal pumping means and the optical signal of the other side distributed by the signal distribution means Gain fixed optical amplifier device comprising a. The method of claim 1, The signal feedback means, Signal distribution means for receiving and distributing the optical signal amplified by the signal amplification means; Variable light attenuation means for variably attenuating the amplified optical signal received from the signal distribution means; And Wavelength selective coupling means for receiving an optical signal attenuated by the variable optical attenuation means and combining the optical signal attenuated by the signal control means to provide an input signal of the signal amplification means; Gain fixed optical amplifier device comprising a. A gain fixed optical amplifier for obtaining a constant gain even for an input signal having a wide wavelength band, Signal feedback means for branching a portion of the signal amplified by the gain fixed optical amplifier and providing it as an input signal of the gain fixed optical amplifier; Signal control means for providing a controlled signal at a constant intensity irrespective of the number of channels of the optical signal received by the signal feedback means; And Signal amplification means for receiving and amplifying a signal controlled by a certain intensity by the signal control means Gain fixed optical amplifier device comprising a. The method of claim 4, wherein The signal feedback means, Signal distribution means for receiving and distributing the optical signal amplified by the signal amplification means; Variable light attenuation means for variably attenuating the amplified optical signal received from the signal distribution means; And A wavelength selective coupling means for receiving an optical signal attenuated by the variable optical attenuating means, combining with an input optical signal from the outside, and providing the optical signal as an input signal of the signal control means; Gain fixed optical amplifier device comprising a. The method of claim 4, wherein The signal control means, Light distribution means for receiving and distributing the output optical signal of the signal feedback means; Signal detection means for receiving an optical signal of one side distributed by the light distribution means and generating an electrical signal proportional to the intensity; Electronic control means for generating an electronic control signal that is linearly inversely proportional to the electrical signal detected by the signal detecting means; Signal pumping means for generating a gain control laser pump light in accordance with an electronic control signal generated by said electronic control means; And A wavelength selective coupling means for combining the laser pump light generated by the signal pumping means with the optical signal of the other side distributed by the signal distribution means and providing it as an input of the signal amplification means; Gain fixed optical amplifier device comprising a. The method according to any one of claims 1 to 6, The signal amplification means, A gain fixed optical amplifier, characterized in that it is a two-stage amplified erbium-doped fiber amplifier (EDFA).