KR100786341B1 - Apparatus for wavelength monitoring - Google Patents

Abstract

A wavelength monitoring apparatus is provided to have a lower loss characteristic to improve the reliability of a communication system. A wavelength monitoring apparatus includes a WDM(Wavelength Division Multiplexing) filter(400) and two photo diode arrays(410,412). The WDM filter has zigzag-shaped adjacent reflection surfaces and a plurality of beam splitters(400-1~400-n), each of which has wavelength dependency reflecting the light of a specific wavelength and passing the light of the rest wavelengths, and reflects the light of different wavelengths to both directions of the serially connected beam splitters. The two photo diode arrays consist of a plurality of photo diodes(410-1,410-3,412-2,412-4) which measure each power of the light of different wavelengths reflected to both directions of the WDM filter.

Description

Wavelength monitoring device {Apparatus for wavelength monitoring}

1 is a schematic configuration diagram of a conventional wavelength monitoring apparatus using a CWDM (Coarse WDM) filter;

FIG. 2 is a cross-sectional view schematically showing a connection relationship between filters when a thin film interference DWDM filter is used in a conventional wavelength monitoring apparatus. FIG.

3 is a view for explaining the principle of a wavelength filter using a beam splitter used in the apparatus of the present invention;

4 is a schematic structural diagram of a wavelength monitoring apparatus according to an embodiment of the present invention;

5 is a schematic structural diagram of a wavelength monitoring apparatus according to another embodiment of the present invention;

FIG. 6 is a view illustrating a state in which a microlens is added to the wavelength monitoring device of FIG. 4 to increase optical coupling efficiency with a photodiode as an optical receiver; FIG. And

FIG. 7 is a view illustrating an appearance of a wavelength monitoring apparatus of the present invention in which the structure of FIG. 4 is manufactured in a package form.

The present invention relates to a wavelength monitoring apparatus, and more particularly, to an apparatus for measuring respective powers after filtering for each wavelength when light having two or more wavelengths enters a receiver in an optical communication system.

BACKGROUND OF THE INVENTION In the field of optical communication, there is a wavelength multiplex communication method in which multiple transmissions of light of a plurality of wavelengths are communicated with an optical fiber, thereby increasing the amount of transmission of information to a greater extent than using a single wavelength of light. In recent years, a wavelength division multiplexing (WDM) communication system that transmits information by simultaneously using laser light sources that generate light having different wavelengths has also been widely used. In such an optical communication system, a wavelength monitoring device is used to identify the wavelength of laser light that transmits and receives. The wavelength monitoring device converts the light from the optical fiber into light arranged by a collimator and passes the light through a device having a wavelength dependency, that is, a wavelength discriminating device whose transmission or reflectance changes with wavelength. A light-receiving element such as a photo diode or the like is used to detect a signal depending on the wavelength. As the wavelength monitoring device, a WDM coupler type as disclosed in U.S. Patent No. 5,822,049, a band pass filter type as disclosed in Japanese Patent Application Laid-open No. Hei 10-253452, or an interferometer type, Etalon Although there is a type, the prior art wavelength monitoring device has a problem that it is difficult to integrate into a small size and low cost. The following examples will discuss in more detail the problems of the prior art.

1 is a schematic configuration diagram of a conventional wavelength monitoring apparatus using a CWDM (Coarse WDM) filter. Referring to FIG. 1, the wavelength monitoring device includes a CWDM filter 100 and an array photodiode 110. CWDM filter 100 is a single filter (100-1, ..., 100-n) is cascaded in the form of a common splicing (splicing) or optical fiber connection (connection), such as the function of wavelength separation Perform. Each of the filters 100-1,..., 100-n transmits light of a specific wavelength according to its characteristics, and light of other wavelengths is incident on a filter of the next stage connected in cascade form. The power of the transmitted light is measured by one of the photodiodes 110-1, 110-2, 110-3,..., 110-n that can sense light of that wavelength. In the case of the wavelength monitoring device having such a configuration, since each device in a single package form is connected to each other only using an optical fiber or the like from the outside, the volume of the CWDM filter 100 increases by 5 cm or more, depending on manual operation. Since there is a problem that the manufacturing cost also increases. In addition, there is a problem of an increase in the packaging volume due to bending for connecting the optical fiber in the packaging.

FIG. 2 is a cross-sectional view schematically illustrating a connection relationship between filters when a thin film interference type DWDM filter is used in a conventional wavelength monitoring apparatus. Referring to FIG. 2, the input signal is an optical signal having eight wavelengths from λ1 to λ8, and has a thin film interference type DWDM filter 230 having a transmission property for light of a specific wavelength and a reflection property for light of another wavelength. ), It is understood that light having a wavelength of λ 4 is obtained as a transmission signal and light having a wavelength of λ 1, λ 2, λ 3, λ 5, λ 6, λ 7, λ 8 is obtained as a reflected signal. The thin film interference type DWDM filter 230 typically uses one formed on a glass substrate. A first GRIN (graded index) lens 220 is used to align the input signal (or the reflected signal) with one end of the DWDM filter 230, and a double ferrule 200 is involved in the connection. In addition, the second GRIN lens 222 is used to align the transmitted signal with the other end of the DWDM filter 230, and a single ferrule 210 is involved in the connection. However, when using such a device, there is a problem in that proper wavelength monitoring is difficult to perform because of large insertion loss.

Accordingly, the technical problem of the present invention is to provide a wavelength monitoring device that can be integrated into a small size and can be manufactured in the form of a chip, thereby reducing the cost of manufacturing and packaging.

Another technical problem of the present invention is to provide a wavelength monitoring device having a low loss characteristic compared to the prior art device.

The present invention for solving the above technical problem, relates to a wavelength monitoring device for measuring each power after filtering the light having a plurality of wavelengths for each wavelength,

Adjacent reflecting surfaces have a plurality of beam splitters connected in series with a zigzag shape, each beam splitter having a wavelength dependency that reflects light of a specific wavelength and passes light of a remaining wavelength. A WDM filter for reflecting light of a wavelength in both directions of the serially connected beam splitters;

Two photodiode arrays comprising a plurality of photodiodes for measuring the power of each of light of different specific wavelengths reflected in both directions of the WDM filter;

Characterized in having a.

At this time, the present wavelength monitoring device includes: an optical fiber for introducing the light having the plurality of wavelengths;

A collimator may be further provided to align light of a plurality of wavelengths introduced through the optical fiber and to enter the WDM filter.

In addition, an additional part such as a micro-lens may be inserted to increase optical coupling efficiency of the photodiode as a receiver.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

3 is a view for explaining the principle of the wavelength filter using a beam splitter used in the apparatus of the present invention, it is shown to help the understanding of the present invention. Referring to FIG. 3, light having wavelengths of λ 1 and λ 2 is incident on a beam splitter 300 having wavelength dependence. The beam splitter 300 reflects light having a λ 1 wavelength and transmits light having a λ 2 wavelength. By doing so, it acts as a wavelength filter.

4 is a schematic configuration diagram of a wavelength monitoring apparatus according to an embodiment of the present invention. Referring to FIG. 4, an optical signal having a plurality of wavelengths λ 1, λ 2,..., Λ n is introduced through the input optical fiber 402, and the light having the plurality of wavelengths introduced through the input optical fiber 402 may be a collimator; Aligned with 405 and incident on WDM filter 400. The WDM filter 400 includes first beam splitters 400-1 to n-th beam splitters 400-n connected in series with adjacent reflection surfaces in a zigzag form. Each beam splitter is configured to mount and coat a filter having a wavelength dependency that reflects light of a particular wavelength and passes light of the remaining wavelength. Adjacent reflecting surfaces have a zigzag shape and light of different wavelengths is reflected in both directions of the WDM filter 400 by a structure connected in series. The reflected light having a specific wavelength includes the first photodiode array 410 including the first group photodiodes 410-1, 410-3,..., And the second group photodiodes 412-2, 412-4,. The power is detected as an electrical signal by each photodiode corresponding to the second photodiode array 412. When the WDM filter 400, the first photodiode array 410, and the second photodiode array 412 are configured in a dual in-line package (DIP) method, an extremely miniaturized wavelength monitoring device may be implemented. In addition, simultaneous individual power detection of multi-wavelength signals is easy, and significant improvements in production cost and package size are possible.

Reference numeral 450, which is not described in the drawings, denotes a positive electrode / negative electrode for operating an individual photodiode, 451 denotes a ground connection when the package is packaged, 452 denotes a power supply voltage (Vcc), and 460 denotes a package body.

In addition, a series connection of a typical single filter accumulates an insertion loss (about 0.3 dB), a connection loss (0.1 dB), and an optical fiber bending loss in a package. For example, connecting eight single filters will result in approximately 3dB of loss. On the contrary, if the WDM filter having the same structure as in the wavelength monitoring apparatus of the present invention is used, even if both the ideal insertion loss (about 0.3 dB) and the loss due to optical signal transmission and the alignment loss are combined, a loss of about 1 dB occurs. In the case of the smallest optimal process, there is no loss other than the loss of each filter, and the size can be made in the unit of mm or less according to the device process, and the bending loss of the optical fiber is not considered because the optical fiber is not required in the package. As a result of the integration technology, it can be realized with a small loss regardless of the number of wavelengths. Moreover, in the case of multi-wavelength simultaneous measurement using the present invention, a receiver and a monitoring system capable of multi-wavelength simultaneous measurement can be used as a main function in an application, and the market is expected to be quite large.

5 is a schematic configuration diagram of a wavelength monitoring apparatus according to another embodiment of the present invention. When comparing the wavelength monitoring device shown in FIG. 5 with that of FIG. 4, the only difference is that the wavelength monitoring device shown in FIG. 4 is used for an end terminal, and performs a function of measuring power for each wavelength, thereby measuring a power meter. It is applied to equipment, etc., the wavelength monitoring device shown in Figure 5 is that the transmission type mainly for use in monitoring. Therefore, description of redundant portions will be omitted. 4 and 5, input light is not transmitted in FIG. 4, but in FIG. 5, most of the light signals except for the optical signal used for monitoring are transmitted through the output optical fiber 403. Here, it is understood that the transmitted optical signal has a plurality of wavelengths λ1, λ2, ..., λn similarly to the input optical signal, but the optical power of the transmitted optical signal is naturally lowered due to monitoring.

Such a wavelength monitoring device of the present invention may be manufactured as a wavelength monitoring chip to be mounted on a PCB substrate. That is, an electronic device-based package such as DIP can be used and can be used as a multi-wavelength simultaneous detection device.

FIG. 6 is a view illustrating a state in which a microlens is added to increase optical coupling efficiency with a photodiode as an optical receiver in the wavelength monitoring apparatus of FIG. 4. Referring to FIG. 6, it can be seen that the optical coupling efficiency is increased by adding a microlens on the optical path through which light emitted from the beam splitter is incident to the photodiode. The micro lenses are installed to correspond to each of the plurality of beam splitters and photo diodes in a 1: 1 manner, so that the micro lenses form an array. For example, the optical coupling efficiency of the optical signal incident from the first beam splitter 400-1 to the first photo diode 400-1 of the first group photo diodes 410-1, 410-3,. In order to increase, the first micro lens 700-1 is provided on the optical path of the optical signal. The device shown in FIG. 6 allows simultaneous individual power detection of multi-wavelength signals, which means that the device of the present invention can be applied to DeMux applications.

FIG. 7 is a view illustrating an appearance of a wavelength monitoring apparatus of the present invention having the structure of FIG. 4 manufactured in a package form. For clarity of illustration, the right side of the package body 460 is shown transparently in FIG. 5. In FIG. 5, A represents Anode and C represents cathode.

Such a wavelength monitoring device of the present invention, wavelength fractionation monitoring, Fiber to The Home (FTTH), Reconfigurable Optical Add / Drop Multiplexers (ROADM), wavelength dependent power detection, loop-back monitoring, power meter, parallel It can be widely used for interface (connector) and the like.

Since the apparatus of the present invention can perform the function of measuring the optical power for each wavelength, it is natural that not only the optical power representing a simple physical quantity but also the function of measuring the power of an optical signal including valid information can be performed. Therefore, the apparatus of the present invention can be widely applied to the field of optical communication.

By using the present invention as described above, it is possible to reduce the cost of manufacturing and packaging the wavelength monitoring device, which is economically advantageous and can implement a wavelength monitoring device having lower loss characteristics than the prior art device. The reliability of the entire communication system including the device can be improved.

Claims (3)

In the wavelength monitoring device for filtering the light having a plurality of wavelengths for each wavelength and measuring each power, Adjacent reflecting surfaces include a plurality of beam splitters connected in series with a zigzag shape, each beam splitter having a wavelength dependency of reflecting light of a specific wavelength and passing light of a remaining wavelength, thereby allowing light of different specific wavelengths to pass through. A WDM filter for reflecting in both directions of the series-connected plurality of beam splitters; Two photodiode arrays comprising a plurality of photodiodes for measuring the power of each of light of different specific wavelengths reflected in both directions of the WDM filter; Wavelength monitoring device having a. The method of claim 1, An optical fiber for introducing the light of the plurality of wavelengths; A collimator for aligning light of a plurality of wavelengths introduced through the optical fiber and injecting the light into the WDM filter; Wavelength monitoring device further comprising. The wavelength monitoring device of claim 1, further comprising a micro lens for increasing optical coupling efficiency on an optical path through which light from each of the plurality of beam splitters enters each of the plurality of photodiodes. .

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