KR19990011795A - All-optical branch coupling device using optical fiber grating element and polarization spectrometer - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an all-optical coupling device, which is a functional element capable of adding or deleting respective channels of consecutive signals at any point between a transmitting end and a receiving end of a wavelength division multiplexing (WDM) system. By configuring the all-optical branch coupling device using, it is possible to obtain a very stable and low-loss optical output without using the special stabilization method used in the past, and also compared to the all-optical branch coupling device using the circulator, Because it can be configured at a price, it has economic advantages,

Description

All-optical branch coupling device using optical fiber grating element and polarization spectrometer

The present invention relates to an all-optical coupling device which is a functional element capable of adding or deleting respective channels of consecutive signals at any point between a transmitting end and a receiving end of a wavelength division multiplexing (WDM) system. The present invention relates to an all-optical branch coupling device using an optical fiber grating element and a polarization spectrometer that improves the stability of an all-optical coupling device by making it using an optical fiber grating device and a polarization spectrometer.

Currently, optical communication systems are being actively researched with increasing importance of high-speed information communication networks all over the world.

In particular, the Wavelength Division Multiplex (WDM) system, which utilizes wavelength multiplexing, is expected to be put to practical use soon because high-density communication is possible due to high optical information density.

Already in Korea, the development of 10bit / s optical transmission system has been actively studied beyond 2.5Gbit / s optical transmission system.

The core technologies of the optical transmission WDM system are the stabilization of the variable light source and frequency, the broadband optical amplifier, the design of the optical link, and the development of the device for the WDM system. The core of the WDM system elements is the transmitting and receiving end of the WDM system. It is an all-optical coupling device that is a device with the ability to add or delete each channel of consecutive signals at any point in between.

Fiber Bragg gratings, which are already being actively studied around the world, have very good characteristics as optical filters due to their very small insertion loss and high wavelength selectivity.

However, since the optical fiber grating element is basically a band-rejection filter, various techniques are required to use it as an all-optical branch coupling device that is a band-pass filter. Branch coupling devices include Mach-Zehnder interferometer type, circulator type and coupler type.

However, such devices have disadvantages of low light output stability, inability to manufacture, or high cost.

Referring to the Makch-Gender interferometer type of the all-optical coupling device, this is a case where the all-optical coupling device is configured by inserting the same optical fiber grating element into the two arms, which is output through the output terminal and the branch terminal due to the use of the interferometer. Since the light output is not constant, it is necessary to match the optical path difference of the two arms.

In this case, stabilization methods such as UV trimming should be used, which is a very difficult and difficult task.

The present invention has been made in view of the conventional problems as described above, and an object of the present invention is to implement an all-optical coupling device using an optical fiber grating element and a polarization spectrometer. This method does not use an interference phenomenon, but rather polarization of two lights. Because of the use of state, it has the advantage of showing very stable characteristics without using a special stabilization method.

BRIEF DESCRIPTION OF THE DRAWINGS The figure explaining the method of manufacturing a general optical fiber grating element.

2 is a view for explaining the principle of operation of the all-optical coupling device of the present invention using a polarization spectrometer when the incident light has a polarization state.

3 is a view for explaining the principle of operation of the all-optical coupling device of the present invention using a polarization spectrometer when the incident light has an arbitrary polarization state.

4 is a view showing the configuration of an all-optical branch coupling device according to the present invention.

* Explanation of symbols for main parts of the drawings

11: optical fiber grating element, 20,22,25: polarization atmosphere, 21,23,24,26,27: polarization regulator

In order to achieve the above object, the present invention provides a polarization spectrometer for separating incident light, a polarization controller for adjusting output characteristics of light separated from the polarization spectrometer, and light passing through each polarization spectrometer. Optical splitting means for splitting light through the optical fiber grating element for filtering;

And a light coupling means for coupling the light through the polarization spectrometer for adjusting the characteristics of the light output from the light splitting means, and a polarization spectrometer for coupling the light and the incident light through the polarization controller.

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.

1 is a view for explaining a general manufacturing method of the optical fiber grating device to be used in the present invention, the optical fiber grating device is manufactured using the optical fiber grating device and the phase mask.

The optical fiber grating element 11 permanently inscribes the periodic refractive index change by using an excimer laser (KrF or ArF excimer laser) 13 in the ultraviolet region in the core 12 of the optical fiber, so that the optical fiber is Likewise, the material is designed to show reflection characteristics for light having a wavelength determined by a period of refractive index change.

[Equation 1]

The phase mask 14 is a kind of diffractive optical element, and serves to separate the applied light according to the diffraction direction of various orders.

By adjusting the height 15 of the optical fiber grating inscribed in the phase mask 14, the zero-order diffraction pattern of ultraviolet laser light incident perpendicularly to the phase mask 14 is suppressed to within an amount of several percent.

As a result, most of the laser power is diffracted in the ± 1st order direction, and the light diffracted in this direction causes interference in the core 12 of the optical fiber, thereby forming an optical fiber grating in the optical fiber.

When explaining the basic principle of the filter of the all-optical coupling device to be manufactured in the present invention by using the optical fiber grating device manufactured in the above manner, and the polarization spectrometer that is commonly used, this is when the incident light has a linearly polarized state Can be divided into and if not.

FIG. 2 is a view for explaining a case of having a polarization state in the above case, and when light having a linear polarization state is incident in the vertical direction as shown in the drawing, the light proceeds to one arm only through the polarization spectrometer 20. do.

The light propagated only by one arm is changed into a circularly polarized light while passing through the λ / 4 polarization controller 21, and the polarization rotation direction of the circularly polarized state is reversed while being reflected by the optical fiber grating element 11.

The emitted light is changed once again through the polarization controller 21, and the polarization state is changed to linearly polarized light. This time, light with a linear linear polarization is incident and exits to a terminal other than the incident terminal (INPUT) ( OUTPUT).

For this reason, light having a linearly polarized state may form a filter using only one optical fiber grating element 11.

3 is a block diagram showing the configuration of a filter for light having an arbitrary polarization state, in which solid lines represent incident light and dotted lines represent reflected light.

Light incident on the input terminal INPUT splits into linearly polarized states perpendicular to each other while passing through the polarization spectrometer 22.

The signals split by the two arms pass through the λ / 4 polarization controllers 23 and 24 and change into a circularly polarized state. The direction of the circularly polarized light of the reflected signal from the optical fiber grating element 11 is reversed to pass through the polarization controllers 23 and 24 again.

Therefore, after reflection, the signal is linearly polarized in the vertical direction of the original input signal, and thus light is emitted from the output terminal (OUTPUT).

Accordingly, it can be seen that two identical optical fiber grating elements are required for light having an arbitrary polarization state.

FIG. 4 is a view showing a novel all-optical coupling device implemented by an optical fiber grating element and a polarization spectrometer according to the present invention. Since the all-optical coupling device has to be used for light having an arbitrary polarization state, in FIG. Implementation is required using the described structure.

By symmetrically constructing two filters having such a basic structure, an all-optical branch coupling device can be made.

Also, because the device has a symmetrical structure, a new signal can be added by injecting light with a Bragg wavelength into terminal 3.

And by attaching optical fiber grating elements with Bragg wavelengths for different channels, it is possible to branch or combine many channels at once.

When the structure thereof is described, two optical fiber grating elements 11, four polarization controllers 23, 24, 26 and 27, and two polarization spectrometers 22 and 25 may be implemented.

The wavelength variable laser is input to the port 1 of the all-optical coupling device implemented as described above using an optical signal.

Subsequently, the polarization controllers 23, 24, 26, and 27 are adjusted to obtain the light output having the best characteristics while measuring the spectra at each terminal using an optical spectrum analyzer.

The optical fiber grating all-optical coupling device configured as described above separates the light that does not pass through the optical fiber grating element 11 from the incident light into a branch terminal (DROP), or emits light having the same wavelength as that output from the branch terminal. Input to the coupling terminal (port 3: ADD) to combine with other lights.

Here, the polarization spectrometer 22 is for the light separator, and the polarization spectrometer 23 is used for the light coupling.

As described in detail above, when the all-optical branch coupling device is configured by using a polarization spectrometer and an optical fiber grating element, a very stable and low loss light output can be obtained without using a special stabilization method conventionally used.

In addition, compared to the all-optical branch coupling device using a circulator, it is possible to construct a useful all-optical branch coupling device at a low price, which is accompanied by economic advantages.

In addition, a preferred embodiment of the present invention is disclosed for the purpose of illustration, those skilled in the art will be able to make various modifications, changes, additions, etc. within the spirit and scope of the present invention, such modifications and modifications belong to the following claims You will have to look.

Claims (2)

Splitting the light through a polarization spectrometer separating the incident light, each polarization regulator adjusting the output characteristics of the light separated by the polarization spectrometer, and an optical fiber grating element filtering the light passing through each polarization spectrometer Optical branching means; And a light coupling means for coupling the light through a polarization spectrometer for coupling the light and the incident light through the polarization controller to adjust the characteristics of the light output from the light splitting means. Branch coupling device. The method according to claim 1, And attaching the optical fiber grating elements having Bragg wavelengths suitable for several different channels to the optical branch coupling device to branch or couple many channels at once.