KR20110071766A - Seed light generating apparatus - Google Patents

Abstract

PURPOSE: A seed photo-generating apparatus is provided to more efficiently create the seed light used in the passive optical subscriber network. CONSTITUTION: An optical amplifier(2) creates the amplified spontaneous emission and amplifies to output. A reflective filter(1) comprises a front side back mirror, a backside reflection mirro, and collimates. The reflective receives and filters the light outputted from the optical amplifier through the optical fiber terminal. The reflective filter outputs the light of the fixed wavelet through the optical fiber terminal. The light outputted from the reflective filter is amplified through the optical amplifier and outputted to the seed light.

Description

Seed light generating apparatus

The present invention relates to a light generating device, and more particularly, to a seed light generating device usable in an optical subscriber network.

The present invention is derived from a study conducted as part of the IT growth engine technology development project of the Ministry of Knowledge Economy [Task Management Number: 2007-S-014-03, Task name: Metro-access all-optical integrated network technology development].

As the demand for bandwidth in a telecommunication network is rapidly increasing, various types of subscriber network technologies are being developed. Among them, FTTH (Fiber-To-The-Home), which can provide ultra-wideband services using optical fiber as a transmission medium, It is recognized as the only solution that can accommodate increased bandwidth demand. In particular, the Passive Optical Network (PON) is the most economical way to implement FTTH because the optical path to subscribers consists of passive elements only, and many subscribers can share the optical fiber to the telephone company and the remote node. to be.

PON technology is divided into time-division-multiplexing PON (TDM-PON) and wavelength-division-multiplexing PON (WDM-PON).

Among them, WDM-PON can assign point-to-point communication by allocating separate wavelength for each subscriber, and light source operating irrespective of wavelength is essential for economical implementation of WDM-PON. To this end, various structures and methods for WDMPON systems and light sources have been proposed.

Wavelength-independent light sources, such as Fabry-Perot Laser Diodes (FP-LDs) or Reflective Semiconductor Optical Amplifiers (RSOAs), are available through wavelength division multiplexers / demultiplexers. Since the wavelength of the output light is determined by the injected optical signal, such a light source is called seed light. As a representative example of seed light, a broadband light source (BLS) using an amplified spontaneous emission (ASE) of an optical amplifier such as EDFA (Erbium Doped Fiber Amplifier) is widely used.

In order to operate an optical signal generating light source located at a telephone company or subscriber side, broadband light generated from seed light is spectral-divided by a wavelength division multiplexer / demultiplexer and filtered and input to the optical signal generating light source. In this conventional method, since the loss of optical power inevitably occurs in the spectral splitting process, there is a problem of increasing the total optical power of the seed light to a predetermined level or more.

Accordingly, studies on the structure of the seed light module capable of providing high light output with higher efficiency while using the same optical amplifier have been actively conducted.

As an example for efficient seed light module fabrication, a filter having a periodic response characteristic to a wavelength, that is, a comb filter is used to filter and then re-amplify the amplified spontaneous emission light (ASE) of the optical amplifier. There is. This structure can increase the light output of the required channel, compared to the broadband light source (BLS), which has a flat output in the entire wavelength band, and the filtering effect when the seed light has a narrower bandwidth than the wavelength division multiplexer / demultiplexer used. It is possible to improve transmission quality deterioration.

Comb filters having periodic response to wavelengths that can be used for seed light modules include Fabry-Perot filter, Mach-Zehnder filter and Sagnac filter. Depending on the implementation method, an integrated optical filter or a PLC-type filter, a thin film filter (TFF), a fiber-type filter, a micro-optic filter, etc. There is this.

A representative example of the comb filter used in the seed light module is a method using a waveguide arrayed grating (AWG) or a fiber interleaver as a comb filter, which is relatively expensive, bulky and wavelength stabilized. There is a disadvantage that the size of the control module for the added and complicated.

When using a Fabry Perot filter as a comb filter, the passband and the filter's extinction ratio (or isolation: the ratio between the filter's maximum and minimum values) vary with the filter's reflectance, thus determining the desired seed light bandwidth and extinction ratio, respectively. It is difficult and structurally dependent on temperature, so a stabilization method is required to compensate for this.

In addition, there are known methods using various filter elements, but it is difficult to satisfy both low insertion loss, small modularity, and easy stabilization method.

The problem to be solved by the present invention is to provide a seed light generating device that can more efficiently generate seed light used in the passive optical subscriber network.

Seed light generating device according to a feature of the present invention, an optical amplifier for generating and amplifying and outputting spontaneous emission light; And a reflective filter which receives the light output from the optical amplifier through an optical fiber terminal and filters the light outputted through the optical fiber terminal, and outputs the light having a predetermined wavelength through the optical fiber terminal, and the light output from the reflective filter is amplified by the optical amplifier. It is output as seed light.

According to an embodiment of the present invention, seed light used in a passive optical subscriber network can be generated more efficiently.

In particular, it is possible to reduce the insertion loss of the device caused by the structural problem of the conventional seed light module, and also to suppress the decrease of the passband caused by the spontaneous emission light being filtered twice by the conventional transmission filter and the reflection mirror. have.

In addition, since the light input and output path is one, compared to the existing two-terminal bidirectional device, it is possible to improve the reliability of the filter and the seed light generating device by facilitating mounting of the device for stabilization and temperature control using the same.

In addition, since it is possible to manufacture integrally with other filter elements in the filter module, it is possible to miniaturize the entire filter module and the seed light generating device, and to minimize the optical fiber coupling loss generated by connecting the individual elements. .

In addition, the broadband operation characteristics of the reflective filter having a single terminal can stably provide an output of a very wide wavelength band or several wavelength bands.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. 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.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise.

1 is a structural diagram of a seed light generating device according to an embodiment of the present invention.

As shown in FIG. 1, the seed light generating apparatus 100 according to an exemplary embodiment of the present invention includes a reflective filter 1 and an optical amplifier 2.

The reflective filter 1 has one terminal for input and output, and filters out light of a desired wavelength band from incident light. The reflective filter 1 according to the embodiment of the present invention may also be referred to as a single terminal reflective filter.

The optical amplifier 2 generates and amplifies and outputs spontaneous emission light, and amplifies and outputs the light output from the reflective filter, that is, the single terminal reflective filter 1.

In the single terminal reflective filter 1 according to the embodiment of the present invention, the input and output of light is made through one terminal, and the light is output at periodic wavelength intervals.

The single terminal reflective filter according to the embodiment of the present invention may be implemented in various forms as follows.

2 is a diagram illustrating a structure of a single terminal reflective filter according to a first embodiment of the present invention.

As shown in FIG. 2, the single terminal reflective filter 1 according to the first embodiment of the present invention includes a collimator 10, a front reflective mirror 20, and a rear reflective mirror 30.

The collimator 10 includes a lens unit (not shown) therein, and one optical fiber terminal F1 is connected to the collimator 10. Light incident from the outside through the optical fiber terminal F1 (which is spontaneous emission light generated and amplified by the optical amplifier 2 and outputted) is incident to the collimator 10 and thus is extended by the internal lens part of the collimator 10. And collimated output. In addition, the light incident on the collimator 10 in the direction opposite to the direction of light incident through the optical fiber terminal F1 is focused by the internal lens unit and output through the optical fiber terminal F1.

The front reflecting mirror 20 is located in the direction in which light collimated through the collimator 10 is output, and the rear reflecting mirror 30 is located behind the front reflecting mirror 20 when referred to the direction. The front reflection mirror 20 and the rear reflection mirror 30 reflect the incident light.

In particular, the front reflection mirror 20 has a shape of a periodic repeating pattern consisting of mirror pieces positioned at predetermined intervals, and reflects light collimated and output through the collimator 10. At this time, as the front reflection mirror 20 is made of mirror pieces positioned at predetermined intervals, light collimated from the collimator 10 and outputted to the mirror pieces of the front reflection mirror 20 is reflected. However, light incident between the mirror pieces of the front reflective mirror 20 will pass through the front reflective mirror 20. Hereinafter, for convenience of description, the mirror pieces positioned at predetermined intervals in the front reflection mirror 20 are referred to as "closed portions of the repeating pattern" according to the front reflection mirror 20, and between the mirror pieces. The corresponding part is called the "open part of the repeating pattern".

Light passing through the open portion of the repeating pattern of the front reflection mirror 20 is reflected by the rear reflection mirror 30 located behind the front reflection mirror 20, and the reflected light is again reflected by the front reflection mirror ( Pass the open part of the repeating pattern of 20).

Accordingly, the light collimated by the collimator 10 and output through the closed portion of the repeating pattern of the front reflection mirror 20 and the open reflection portion of the repeating pattern of the front reflection mirror 20 passes through the rear reflection mirror 30. ) And then the light output through the open portion of the repeating pattern of the front reflection mirror 20 can be output through the optical fiber terminal (F1) while being coupled through the collimator 10. In this case, a phase difference is induced between the light reflected by the front reflection mirror 20 and the light reflected by the rear reflection mirror 30 by the relative optical path difference between the two reflection mirrors 20.30, and the periodic interference The pattern is generated. At this time, the extinction ratio can be adjusted by adjusting the area ratio of the open and closed portions of the repeating pattern.

In the single terminal reflective filter 1 according to the first embodiment of the present invention having such a structure, light is inputted and outputted through the same optical fiber terminal F1, and the optical signal of the desired wavelength is selected and the direction of the optical signal is changed. It works by changing the reflection.

When applied to the seed light generating device 100 using the single terminal reflective filter 1 according to the first embodiment of the present invention, it is possible to reduce the loss of light, compared to the conventional seed light generating device, the filter bandwidth This can be prevented from being reduced.

In detail, the conventional seed light generating device includes a comb filter, an optical amplifier, and a reflecting mirror, wherein the light of the broadband light source (BLS) traveling in the opposite direction of the output is disposed at periodic wavelength intervals through the comb filter. It is selected and output as spectral division, and the reflecting mirror reflects this light and reincarnates it through the comb filter into the optical amplifier. Therefore, as the light passes through the comb filter twice through the reflecting mirror, the insertion loss of the light generated by the filter itself increases, and as the reflecting mirror and the comb filter are respectively installed, the light loss in the connection between the filter and the reflecting mirror is reduced. Will occur.

However, in the case of using the single terminal reflective filter according to the embodiment of the present invention having the structure as described above, the light is reflected by the front reflection mirror and the rear reflection mirror included in the filter, so that the filter and the reflection mirror It is possible to prevent light loss caused by external connection. In addition, compared to the existing device in which the light passes through the filter more than once, according to an embodiment of the present invention, the light is reflected only inside the filter, thereby preventing the insertion loss and bandwidth reduction caused by passing through the filter.

Next, a single terminal reflective filter according to a second embodiment of the present invention will be described.

The seed light generating apparatus according to the second embodiment of the present invention is implemented in a form in which the reflective filter further includes at least one filter in order to improve performance.

3 is a diagram illustrating a structure of a single terminal reflective filter according to a second embodiment of the present invention.

As shown in FIG. 3, the single terminal reflective filter according to the second embodiment of the present invention is the same as the first embodiment, the collimator 10, the front reflection mirror 20 and the rear reflection mirror 30 It further comprises, at least one or more internal filters 40 to further improve the performance of the seed light generating device.

Specifically, the single-terminal reflective filter according to the second embodiment of the present invention includes a gain flattening filter as the internal filter 40 so that the spectral split seed light has an equal light output. As the gain flattening filter, a multilayer thin film filter having a permeation characteristic performing a gain flattening function may be used. Meanwhile, the multilayer thin film filter is manufactured to have a wavelength response characteristic with respect to any one of transmitted light and reflected light, which are complementary to each other. Therefore, when the single terminal reflective filter according to the embodiment of the present invention uses the multilayer thin film filter as the internal filter, the light reflected from the multilayer thin film filter is not re-entered into the collimator 10.

The gain flattening filter 40 is positioned between the front reflecting mirror 20 and the collimator 10, and in particular, the gain flattening filter 40 is located at the side where light is reflected from the front reflecting mirror 20 and outputted. And the gain of the spectrum-divided light while being reflected by the rear reflection mirror 30 is flattened and output. Since the gain flattening filter 40 may be formed in a form that can be devised by those skilled in the art, a detailed description of the filter structure is omitted here.

According to the second embodiment of the present invention, an internal filter, that is, a gain flattening filter is positioned inside the single terminal reflective filter to be integrally formed, thereby preventing spectrum loss while preventing optical loss occurring in a method of connecting and manufacturing individual elements. The gain of the divided light can be flattened. Although an example using a filter for flattening the light output is given here, the present invention is not limited to this. For example, a band select filter for limiting the bandwidth of the optical signal to a specific band may be used as the internal filter.

As described above, in the second exemplary embodiment of the present invention, at least one internal filter may be additionally used in the single terminal reflective filter having the same structure as that of the first exemplary embodiment in order to output seed light having a desired output spectrum. .

Next, a single terminal reflective filter according to a third embodiment of the present invention will be described.

4 is a view showing the structure of a single terminal reflective filter according to a third embodiment of the present invention.

As shown in FIG. 4, the single terminal reflective filter according to the third embodiment of the present invention has the same collimator 10, front reflection mirror 20, and rear reflection mirror 30 as in the first embodiment. To include, in order to improve the stabilization characteristics of the filter, further comprises a stabilization unit (50).

Here, the stabilization unit 50 according to the third embodiment of the present invention, the temperature detection unit 51 and the thermo-electric cooler (Thermo-Electric) in order to prevent the optical characteristics of the filter, such as the wavelength of the light selected by the heat is changed. Cooler, 52).

Since the conventional seed light generating device uses a transmission filter element, optical paths are formed at both sides of the filter element, and thus, the stabilization unit is not easily installed in each optical path and its implementation is very complicated. On the contrary, according to the embodiment of the present invention, since the input and output paths of light are the same, the stabilization unit 50 may be more easily installed.

Specifically, in the third embodiment of the present invention, the temperature detector 51 and the thermoelectric cooler 52, which are stabilizers, are located in opposite directions of the optical fiber terminal F1, which is an input / output path of light. That is, when the front direction of the rear reflection mirror 30 is the direction in which the collimator 10 is located, it is located in the rear direction of the rear reflection mirror 30.

In addition, according to the embodiment of the present invention, since there is only one input / output path of light, that is, the input / output of the light is made through the optical fiber terminal F1, thereby easily filtering the temperature detector 51 and the thermoelectric cooler 52 for stabilization. 1) It can be mounted inside and its control is easy.

Here, the temperature detector 51 and the thermoelectric cooler 52 are used as an example. In addition, all the stabilization elements capable of controlling and detecting the optical characteristics of the flat plate inducing the optical path difference may be additionally used, or the temperature detector 51 may be used. And thermoelectric cooler 52.

Of course, the stabilization unit 50 according to the third embodiment may be additionally included even when the single terminal reflective filter 1 is implemented in a form including an internal filter as in the second embodiment.

In addition, the single-terminal reflective filter 1 according to the embodiments described above collimates and outputs the light input through the optical fiber terminal F1 and collects and outputs the light reflected by the reflective mirrors 20 and 30. Although a single fiber type collimator is used as a means, an integrated optical type device using a semiconductor process may be used instead of the collimator.

In addition, in the above embodiments, the optical path difference between the front reflection mirror and the rear reflection mirror is 2nd / λ and sine wave (sine wave) response characteristics to the wavelength is exemplified. In addition to such a path difference, various path differences may be formed together to implement an arbitrary wavelength transmission characteristic.

By using a single terminal reflective filter according to these embodiments it is possible to implement a filter having an arbitrary wavelength transmission characteristics, and to provide a seed light generating device for outputting light in a desired wavelength band using a single terminal reflective filter. Can be. In addition, the seed light generating apparatus according to an embodiment of the present invention can be used as a light source for providing a seed light having a broadband characteristics applied to a plurality of wavelength bands used in the passive optical subscriber network.

Filter and seed light generating apparatus according to an embodiment of the present invention can provide a seed light of economical and excellent performance, it can greatly contribute to the activation and performance enhancement of the optical subscriber network.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a structural diagram of a seed light generating device according to an embodiment of the present invention.

2 is a structural diagram of a reflective filter according to a first embodiment of the present invention.

3 is a structural diagram of a reflective filter according to a second embodiment of the present invention.

4 is a structural diagram of a reflective filter according to a third embodiment of the present invention.

Claims (8)

An optical amplifier for generating, amplifying and outputting spontaneous emission light; Reflective filter for receiving the light output from the optical amplifier through the optical fiber terminal and filtering the output light of the predetermined wavelength through the optical fiber terminal Including, The light output from the reflective filter is amplified through the optical amplifier is output to the seed light, seed light generating device. The method of claim 1, The reflective filter, A collimator for collimating and outputting light input through an optical fiber terminal; A front reflecting mirror which reflects or passes light collimated from the collimator and output; A rear reflection mirror reflecting light output through the front reflection mirror Seed light generating device comprising a. The method of claim 2, The reflective filter, An internal filter positioned between the front reflective mirror and the collimator to filter light output from the front reflective mirror Further comprising, seed light generating device. The method of claim 3, And the internal filter is a gain planarization filter for flattening and outputting the gain of the light. The method of claim 2, The reflective filter, Stabilizer for stabilizing the light output by the reflective filter is located in the opposite direction of the rear reflection mirror toward the front reflection mirror Further comprising, seed light generating device. The method according to any one of claims 2 to 5 The front reflection mirror has a shape of a periodic repeating pattern consisting of a plurality of mirror pieces positioned at predetermined intervals, And the light incident to the closed portion corresponding to the mirror pieces positioned at the predetermined intervals is reflected, and the light incident to the open portion corresponding to the mirror pieces is passed through and output. The method of claim 6 And the collimator focuses the light reflected through the closed portion of the front reflection mirror and the light output through the open portion of the front reflection mirror and outputs the light to the optical fiber terminal. The method of claim 1 The seed light generating device is used as a light source for providing a seed light having a broadband characteristics applied to a plurality of wavelength bands used in a passive optical subscriber network.

Images