KR20110117926A - Apparatus and system for controlling tunable lasers - Google Patents

Abstract

An apparatus for controlling a tunable laser is provided. The optical transmitter for controlling the tunable laser is an output light sensing photodiode for sensing the intensity of the output light output from the tunable laser, the tunable laser is output from the tunable laser, multiplexed through a multiplexer, and then reflected by the multi And a wavelength controller configured to control the wavelength of the output light based on a difference between the intensity of the reflected light and the output light and the reflected light sensing photodiode for sensing the intensity of the reflected light input through the flexor.

Description

APPARATUS AND SYSTEM FOR CONTROLLING WAVELENGTH TUNABLE LASERS}

The present invention relates to an apparatus and system for controlling a tunable laser, and more particularly, to an optical transmitter and a system including the optical transmitter for controlling the laser for wavelength stabilization of the tunable laser.

Recently, attempts to convert existing subscriber networks to FTTH (Fiber to the home) schemes have been actively conducted to accommodate the rapidly increasing amount of Internet data traffic. Among them, FTTH of WDM-PON method is economical and can take full advantage of the transmission band of optical fiber, can provide stable bandwidth for each subscriber, and attracts great attention because of the fact that there is no inherent security problem between subscribers. I am getting it.

In general, in WDM-PON, since a separate wavelength is provided to each subscriber station or an optical network terminator, a low-cost WDM optical transceiver module and system implementation are required.

In addition, in order to reduce the cost of installation and maintenance of the subscriber network, it is preferable that a wavelength independent light source is used so that all subscribers can use the same kind of light source. Such wavelength-independent light sources include a fabric-perot (FP) laser implanted with a seed light source, a reflective semiconductor optical amplifier (RSOA) implanted with a seed light source, or a tunable laser.

In particular, in order to use the tunable laser as a light source of the WDM optical transmission system and the WDM-PON, the oscillation wavelength of the tunable laser must match the transmission wavelength of the wavelength division multiplexer / demultiplexer. In the method and apparatus for multi-wavelength fixing using an acoustooptic wavelength filter), a technique of fixing a wavelength of a light source by applying a pilot signal to an acoustooptic filter and monitoring the output wavelength of the light source is disclosed.

However, this has a problem of providing an expensive acoustooptic filter for each channel or subscriber and observing an optical signal passing through the filter while changing the pass wavelength of the provided acoustooptic filter.

In addition, in the above-described conventional WDM optical transmission system and WDM-PON, in order to match the oscillation wavelength of the tunable laser with the transmission wavelength of the wavelength division multiplexer / demultiplexer, the oscillation wavelength of the tunable laser is manually adjusted, or It uses a look-up table to find the oscillation wavelength.

However, such a manual method or a method using a look-up table has a problem that it is difficult to implement economically because it requires a lot of professional manpower and time.

Therefore, there is a need for a new method for economically realizing the WDM optical transmission system and the WDM-PON by automatically adjusting the oscillation wavelength of the tunable laser.

In order to solve the above-mentioned problems of the prior art, the present invention provides an apparatus for stably and precisely controlling the wavelength of the tunable laser automatically.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood from the following description.

In order to achieve the above object, an optical transmitter for controlling a tunable laser according to an aspect of the present invention, an output light sensing photodiode for sensing the intensity of the output light output from the tunable laser, the output from the tunable laser And a reflected photodiode for detecting the intensity of the reflected light input through the multiplexer and reflected by multiplexing through the multiplexer, and based on a difference between the intensity of the detected reflected light and the output light, And a wavelength controller for controlling the wavelength of the output light.

In order to achieve the above object, an optical communication system according to an aspect of the present invention comprises a plurality of optical transmitters including a wavelength tunable laser, a multiplexer for multiplexing the output light of different wavelengths output from the plurality of optical transmitters; A reflection device connected to an output terminal of the multiplexer to reflect the output light of the multiplexer to the multiplexer, wherein the optical transmitter is configured to reflect the intensity of the reflected light reflected by the reflection device and the wavelength tunable laser; The wavelength of the output light is controlled based on the difference in the intensity of the output light.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG.

The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. It is provided to fully inform the owner of the scope of the invention.

According to one of the problem solving means of the apparatus and system for controlling the tunable laser of the present invention described above, the wavelength of the tunable laser can be controlled automatically and stably.

In addition, the tunable lasers of all wavelength channels share one common reflecting mirror or Fabry-Perot filter to reduce the additional cost of the system.

1 is a diagram showing the configuration of a system for controlling a tunable laser according to an embodiment of the present invention.
2 is a diagram illustrating a configuration of a system for controlling a tunable laser according to another embodiment of the present invention.
3 is a diagram illustrating a configuration of a system for controlling a tunable laser according to another embodiment of the present invention.
4 is a block diagram showing the configuration of an optical transmitter according to an embodiment of the present invention.
5 is a diagram illustrating a method of controlling a wavelength in a wavelength controller according to an embodiment of the present invention.
6 is a diagram illustrating a method of controlling a wavelength in a wavelength controller according to another exemplary embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

For reference, in the entire specification, when a part is "connected" to another part, it is not only "directly connected" but also "electrically connected" with another element in between. Also includes.

Also, when an element is referred to as "comprising ", it means that it can include other elements as well, without departing from the other elements unless specifically stated otherwise.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

1 is a diagram showing the configuration of a system for controlling a tunable laser according to an embodiment of the present invention.

A system for controlling a tunable laser according to an embodiment of the present invention includes an optical transmitter 110, a multiplexer 120, an optical power divider 130, a reflective mirror 141, a demultiplexer 150 and an optical receiver ( 160).

In describing each component, a plurality of optical transmitters 110 are each connected to the multiplexer 120, and each optical transmitter 110 scans the center wavelength of a specific channel with respect to the multiplexer 120.

In more detail, the optical transmitter 110 transmits output light to the multiplexer 120 while changing the wavelength by a predetermined wavelength (? Λ). In this case, the optical transmitter 110 may detect the intensity of the output light and control the intensity of the output light so that the detected output light maintains a constant intensity.

Thereafter, the optical transmitter 110 receives the reflected light of the center wavelength of the specific channel reflected from the multiplexer 120 through the reflection mirror 141.

In this case, the optical transmitter 110 may include an isolator in order to prevent signal quality degradation due to the reflective characteristics of the reflective mirror 141.

For reference, the multiplexer 120 generates maximum reflection at the center wavelength of a specific channel. Accordingly, the optical transmitter 110 senses the wavelength and intensity of the reflected light input through the reflective mirror 141, and the difference between the intensity of the input reflected light and the intensity of the output light is minimal with respect to the transmission characteristics of the multiplexer 120. The wavelength of the output light is controlled (adjusted) so that.

In this case, the difference between the intensity of the input reflected light and the intensity of the output light means an absolute value.

Transmission characteristics of the multiplexer 120 and wavelength control of the optical transmitter 110 will be described later with reference to FIG. 5.

Thereafter, the optical transmitter 110 transmits the output light to the multiplexer 120 at the adjusted wavelength, and if the channel is changed, scans the center wavelength of the changed channel, and passes the above-described process to correct the channel. Know the wavelength.

For reference, the optical transmitter 110 may operate as a module included in an optical transceiver. That is, the implementation of the form in which the optical transceiver replaces the optical transmitter 110 is sufficiently possible.

On the other hand, the multiplexer 120 transmits the output light having a predetermined specific wavelength among the output light input from the optical transmitter 110, the maximum reflection occurs at the specific wavelength transmitted, that is, the center wavelength of the specific channel do.

In addition, the multiplexer 120 receives the reflected light of the center wavelength for the specific channel from the reflection mirror 141, and transmits it to the optical transmitter 110.

On the other hand, the optical power splitter 130 is located at the output terminal of the multiplexer 120, the demultiplexer 150 and the reflecting mirror 141 to output the light having a specific wavelength transmitted from the multiplexer 120 To distribute.

In this case, the ratio of output light distributed from the optical power splitter 130 to the demultiplexer 150 and the reflective mirror 141 may be set differently according to an embodiment.

If the ratio of output light distributed to the reflective mirror 141 is low, the optical transmitter 110 uses an expensive sensitive reflected light detection photodiode to detect the wavelength and intensity of the reflected light input through the reflective mirror 141. Can be used.

On the contrary, when the ratio of output light distributed to the reflective mirror 141 is high, the optical transmitter 110 is distributed to the reflective mirror 141 to sense the wavelength and intensity of the reflected light input through the reflective mirror 141. A less sensitive and inexpensive photodiode for detecting reflected light can be used than if the ratio of output light is low.

Therefore, in consideration of the advantages and disadvantages described above, the ratio of the output light distributed from the optical power splitter 130 to the demultiplexer 150 and the reflection mirror 141 may be set.

On the other hand, the reflective mirror 141 receives a portion of the output light from the optical power splitter 130 and reflects, but a portion of the input output light ratio in advance to the output light input to the optical power splitter 130 as described above This can be determined.

2 is a diagram illustrating a configuration of a system for controlling a tunable laser according to another embodiment of the present invention.

A system for controlling a tunable laser according to another embodiment of the present invention includes an optical transmitter 110, a multiplexer 120, an optical power divider 130, a circulator 142, and a Fabry-Perot. Perot) filter 143, demultiplexer 150 and optical receiver 160.

In describing each component, a plurality of optical transmitters 110 are each connected to the multiplexer 120, and each optical transmitter 110 scans the center wavelength of a specific channel with respect to the multiplexer 120.

In more detail, the optical transmitter 110 transmits output light to the multiplexer 120 while changing the wavelength by a predetermined wavelength (? Λ).

Thereafter, the optical transmitter 110 receives the reflected light of the center wavelength of the specific channel reflected from the multiplexer 120 through the circulator 142.

As described above, since the multiplexer 120 generates the maximum reflection at the center wavelength of a specific channel, the optical transmitter 110 is a circulator 142 and a Fabry-Perot filter (hereinafter referred to as FP filter). The wavelength and intensity of the reflected light input through the 143 is sensed, and the difference between the intensity of the reflected light and the intensity of the output light is obtained by using the transmission characteristics of the multiplexer 120 and the transmission characteristics of the FP filter 143. The wavelength of the output light is adjusted so that is minimized.

The transmission characteristics of the multiplexer 120 and the transmission characteristics of the FP filter 143 will be described later with reference to FIG. 6.

For reference, the optical transmitter 110 may operate as a module included in an optical transceiver. That is, the implementation of the form in which the optical transceiver replaces the optical transmitter 110 is sufficiently possible.

On the other hand, the multiplexer 120 transmits the output light having a predetermined specific wavelength among the output light input from the optical transmitter 110, the maximum reflection occurs at the center wavelength of the specific channel.

In addition, the multiplexer 120 receives the reflected light of the center wavelength for the specific channel from the circulator 142 and transmits it to the optical transmitter 110.

On the other hand, the optical power divider 130 is located at the output terminal of the multiplexer 120 to distribute the output light having a specific wavelength transmitted from the multiplexer 120 to the demultiplexer 150 and the circulator 142.

In this case, the ratio of output light distributed from the optical power divider 130 to the demultiplexer 150 and the circulator 142 may be set differently according to an embodiment.

Meanwhile, the circulator 142 receives a part of the output light from the optical power splitter 130 and transmits it to the FP filter 143, and the output light filtered by the FP filter 143 is output to the output terminal of the multiplexer 120. Prevent the return.

The circulator 142 includes a first port connected to the output terminal of the optical power splitter 130, a second port connected to the input terminal of the FP filter 143, and a third port connected to the output terminal of the FP filter 143. do.

Meanwhile, the FP filter 143 transmits the output light input from the circulator 142 and transmits the output light back to the circulator 142.

For reference, the FP filter 143 transmits only an optical signal having a specific wavelength, and has a transmission characteristic capable of setting a wavelength width and a period of the transmitted optical signal.

Therefore, when the wavelength period of the FP filter 143 is the same as the wavelength period of the multiplexer 120, and the wavelength width of the FP filter 143 is set to be narrower than the transmission band of the multiplexer 120, the light The transmitter 110 may precisely control the wavelength of the output light input from the circulator 142 through the FP filter 143.

That is, when the optical transmitter 110 scans the multiplexer 120 in real time for wavelength control, the wavelength of the output light is out of the transmission band of the multiplexer 120, or the intensity of the output light is multiplexer ( The problem that is changed every time due to the loss of 120 can be solved through the system shown in FIG. 2.

3 is a diagram illustrating a configuration of a system for controlling a tunable laser according to another embodiment of the present invention.

In another embodiment of the present invention, a system for controlling a tunable laser includes an optical transmitter 110, a multiplexer 120, an optical power divider 130, an FP filter 144, a reflection mirror 145, and a demultiplexer. 150 and optical receiver 160.

The configuration of the system shown in FIG. 3 replaces the circulator 142 and the FP filter 143 with the FP filter 144 and the reflection mirror 145 among the components of the system shown in FIG. The description of the components will be omitted.

For reference, it is to be understood that the remaining other components shown in FIG. 3, which are not described below, naturally operate in conjunction with the FP filter 144 and the reflecting mirror 145.

The FP filter 144 receives a part of the output light from the optical power splitter 130 and transmits it to the reflective mirror 145.

In addition, the FP filter 144 receives the output light reflected from the reflection mirror 145 and transmits it to the multiplexer 120.

The reflection mirror 145 receives the output light from the FP filter 144 and reflects the output light to the FP filter 144.

That is, the system shown in FIG. 3 performs two filtering processes using the FP filter 144 and the reflecting mirror 145, thereby allowing the optical transmitter 110 to control the wavelength more precisely.

4 is a block diagram showing the configuration of an optical transmitter 110 according to an embodiment of the present invention.

The optical transmitter 110 for controlling the tunable laser according to an embodiment of the present invention includes a tunable laser 111, an optical power divider 112, a photodiode 113 for output light sensing, a power controller 114, And a photodiode 115 and a wavelength controller 116 for detecting the reflected light.

For reference, components 111 to 116 of the optical transmitter 110 illustrated in FIG. 4 may be included in the optical transceiver.

In describing each component, the wavelength tunable laser 111 transmits output light to the multiplexer 120. In addition, the tunable laser 111 transmits the output light with the power (intensity) adjusted by the power control unit 114.

In addition, the tunable laser 111 may include an isolator in order to prevent signal quality degradation due to reflection characteristics of the reflection mirror 141 in the system shown in FIG. 1.

Meanwhile, when the optical power divider 112 transmits the output light from the wavelength tunable laser 111 to the multiplexer 120, the optical power divider 112 transmits the output light to the multiplexer 120 and the photodiode 113 for output light sensing. Distribute each.

In this case, the ratio of the output light distributed from the optical power divider 112 to the multiplexer 120 and the output light sensing photodiode 113 may be set differently according to an embodiment.

In addition, the optical power divider 112 receives the reflected light from the multiplexer 120 and transmits the reflected light to the photodiode 115 for detecting the reflected light.

On the other hand, the output light sensing photodiode 113 receives a portion of the output light from the optical power splitter 112, detects the intensity of the input output light and transmits the corresponding intensity information to the power control unit 114.

On the other hand, the power control unit 114 receives information on the intensity of the output light from the photodiode 113 for output light sensing, and controls the intensity of the output light so that the output light maintains a predetermined constant intensity.

Meanwhile, the reflected light detecting photodiode 115 receives the reflected light from the optical power divider 112, detects the wavelength and intensity of the received reflected light, and transmits the wavelength and intensity information of the reflected light detected by the wavelength controller 116. .

At this time, the reflected light input by the reflected light detecting photodiode 115 is reflected mirror 141 shown in FIG. 1, the circulator 142 and FP filter 143 shown in FIG. 2, or the FP filter shown in FIG. 3. 144 and reflective mirror 145.

The wavelength controller 116 controls (adjusts) the wavelength of the output light based on the difference between the intensity of the input reflected light and the intensity of the output light.

The wavelength control of the wavelength controller 116 will be described later with reference to FIGS. 5 and 6.

For reference, the components illustrated in FIG. 4 according to an embodiment of the present invention mean software components or hardware components such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC), and perform predetermined roles. .

However, 'components' are not meant to be limited to software or hardware, and each component may be configured to be in an addressable storage medium or may be configured to reproduce one or more processors.

Thus, by way of example, an element may comprise components such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, Routines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables.

Components and the functionality provided within those components may be combined into a smaller number of components or further separated into additional components.

5 is a diagram illustrating a method of controlling a wavelength in the wavelength controller 116 according to an embodiment of the present invention.

The wavelength control method shown in FIG. 5 is a method using the reflection mirror 141 of the system shown in FIG.

When the transmission characteristic 510 of the multiplexer 120 is as shown in FIG. 5, the wavelength controller 116 transmits the transmission characteristic 510 of the multiplexer 120 to retrieve the center wavelength for a specific channel. ), The wavelength of the output light can be adjusted.

For example, as illustrated in FIG. 5, when the wavelength of the output light is λ 1, the wavelength controller 116 adjusts the direction λ 2 to increase the wavelength of the output light, so that the difference between the intensity of the input reflected light and the intensity of the output light is different. The band 520 of the transmission characteristic 510 of the multiplexer 120 to be minimized is searched.

That is, when the wavelength of the output light increases, the difference between the intensity of the input reflected light and the intensity of the output light decreases according to the transmission characteristic 510 of the multiplexer 120.

In addition, when the wavelength of the output light is λ3, the wavelength control unit 116 adjusts in the direction of decreasing the wavelength of the output light (λ4), the multiplexer 120 to minimize the difference between the intensity of the input reflected light and the output light Search for the band 520 of the transmission characteristic 510.

That is, when the wavelength of the output light is reduced, the difference between the intensity of the input reflected light and the intensity of the output light is reduced according to the transmission characteristic 510 of the multiplexer 120.

For reference, since the intensity of the output light is constant, even if the wavelength controller 116 increases or decreases the wavelength of the output light, the difference between the intensity of the input reflected light and the intensity of the output light decreases according to the transmission characteristics 510 of the multiplexer 120. Done.

As described above, the wavelength control unit 116 increases or decreases the wavelength of the output light, and the band 520 of the transmission characteristic 510 of the multiplexer 120 having the minimum difference between the intensity of the input reflected light and the output light is minimized. By searching for, the wavelength of the output light can be adjusted to the center wavelength for a specific channel.

6 is a diagram illustrating a method of controlling a wavelength in the wavelength controller 116 according to another embodiment of the present invention.

The wavelength control method shown in FIG. 6 is a method using the FP filters 143 and 144 of the system shown in FIG. 2 or 3.

6 illustrates the transmission characteristics of the FP filters 143 and 144, that is, the width and the period of the transmitted wavelength, when the transmission characteristics 610 of the multiplexer 120 are illustrated in FIG. 6. This is the case where the wavelength width of the FP filters 143 and 144 is set narrower than the transmission band of the multiplexer 120 in the same manner as the wavelength period of 120.

In FIG. 6, the wavelength controller 116 may increase the wavelength of the output light to search for the center wavelength for a specific channel. At this time, the difference between the intensity of the input reflected light and the intensity of the output light decreases according to the transmission characteristics 620 of the FP filters 143 and 144.

In addition, the wavelength controller 116 may reduce the wavelength of the output light to search for the center wavelength for the specific channel. At this time, the difference between the intensity of the input reflected light and the intensity of the output light decreases according to the transmission characteristics 620 of the FP filters 143 and 144.

For reference, since the intensity of the output light is constant, even if the wavelength controller 116 increases or decreases the wavelength of the output light, the difference between the intensity of the input reflected light and the intensity of the output light depends on the transmission characteristics 620 of the FP filters 143 and 144. Will decrease.

As described above, the wavelength controller 116 increases or decreases the wavelength of the output light and minimizes the difference between the intensity of the reflected light and the output light, that is, the center of the transmission wavelength of the multiplexer 120 and the FP. By searching the contact point 630 of the transmission wavelength center of the filter (143, 144), the wavelength of the output light can be adjusted to the center wavelength for a particular channel.

In this case, the narrower the transmission characteristics of the FP filters 143 and 144, the more precisely the wavelength controller 116 may adjust the wavelength of the output light to the center wavelength for the specific channel.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is shown by the following claims rather than the above description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

111: tunable laser
112: Optical Power Divider
113: photodiode for output light detection
114: power control unit
115: photodiode for detecting reflected light
116 wavelength control unit

Claims (12)

An optical transmitter for controlling a tunable laser,
An output light sensing photodiode sensing the intensity of the output light output from the wavelength tunable laser,
A reflected light sensing photodiode output from the wavelength tunable laser, multiplexed through a multiplexer, and reflected to detect an intensity of reflected light input through the multiplexer;
A wavelength controller configured to control a wavelength of the output light based on the detected difference between the intensity of the reflected light and the intensity of the output light
Including, the optical transmitter.
The method of claim 1,
And the wavelength controller adjusts the wavelength of the output light to minimize the difference between the sensed intensity of the reflected light and the intensity of the output light based on the transmission characteristics of the multiplexer.
The method of claim 2,
The wavelength controller reduces the wavelength of the output light when the wavelength of the output light is greater than the center wavelength of a specific channel based on the transmission characteristics of the multiplexer, and when the wavelength of the output light is smaller than the center wavelength of the specific channel. And increasing the wavelength of the output light to adjust the wavelength of the output light so that the difference between the sensed intensity of the reflected light and the intensity of the output light is minimized.
The method of claim 3, wherein
The intensity of the output light is fixed, and the intensity of the sensed reflected light is varied according to the adjustment of the wavelength.
The method of claim 1,
And the reflected light is reflected through a reflecting mirror.
The method of claim 1,
Wherein the reflected light is reflected through a circulator and a Fabry-Perot filter connected to the circulator.
The method of claim 1,
Wherein the reflected light is reflected through a Fabry-Perot filter and a reflecting mirror connected to the Fabry-Perot filter.
In the optical communication system,
A plurality of optical transmitters comprising a tunable laser,
A multiplexer for multiplexing output light having different wavelengths output from the plurality of optical transmitters;
A reflection device connected to an output terminal of the multiplexer to reflect output light of the multiplexer to the multiplexer
Including, wherein the optical transmitter controls the wavelength of the output light based on a difference between the intensity of the reflected light reflected through the reflecting device and the intensity of the output light output from the wavelength tunable laser.
The method of claim 8,
The reflecting device comprises a reflecting mirror.
The method of claim 8,
The reflecting device includes a circulator and a Fabry-Perot filter connected to the circulator.
The method of claim 8,
The reflecting device comprises a Fabry-Perot filter and a reflecting mirror connected to the Fabry-Perot filter.
The method according to any one of claims 9 to 11,
The reflector receives and reflects a portion of the output light from an optical power divider located at an output end of the multiplexer, but a portion of the output light input to the reflector is a predetermined ratio with respect to the output light input to the optical power divider. Optical communication system.

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