CN1750446A - OADM - Google Patents

Abstract

This invention provides an optical add-drop multiplexer (OADM) including an OADM, ports of input and output and ports of up path and down path, among which, the OADM is in the array of several MEMS optical switches composed of a microlens and a driving device, the microlens is a multiple medium film filter laminated alternately by multiplayer films with high or low refractive rates, only a specific wavelength is reflected while others are transmitted when the multiplex wavelength radiates the microlens. When the driving device starts the microlens related to the specific wavelength on MEMS optical switch array, the up and down paths of said specific wavelength in WDM signals can be realized.

Description

OADM

technical field

The invention belongs to the technical field of optical fiber communication, and in particular relates to an optical add/drop multiplexer (OADM: Optical add/drop multiplexer).

Background technique

Dense Wavelength Division Multiplexing (DWDM) optical communication network has become the current development trend of communication network due to its obvious advantages such as high speed and large bandwidth. OADM is one of the core devices that constitute the DWDM all-optical network. Its main function is to selectively drop (drop) the local optical signal from the transmission equipment, and at the same time add (add) the optical signal sent by the local user to another node user. signal without affecting the transmission of other wavelength channels. The optical add-drop multiplexer completes the switching function originally performed by the electrical switching equipment in the optical domain, overcomes the electronic bottleneck of optical-electrical-optical conversion, and makes the optical fiber communication network flexible, selective, transparent, and scalable and reconfigurability and other superior features. Moreover, the use of OADM can also improve the reliability of the optical network, reduce node costs, and improve network operation efficiency. Therefore, OADM has become one of the key technologies for establishing a DWDM all-optical network.

At present, there are mainly the following schemes for realizing OADM: based on demultiplexing/multiplexing structure, based on fiber Bragg grating structure, based on optical fiber circulator structure, and based on acousto-optic tunable filter structure. Among them, the OADM based on the demultiplexing/multiplexing structure has a good development prospect and has become a research hotspot in recent years.

Contents of the invention

Based on the research of demultiplexing/multiplexing structure OADM, the present invention provides an OADM with simple control, low cost, small insertion loss, high channel isolation, simple and compact structure, and easy integration. The OADM is insensitive to incident light polarization, No need for a separate demux/mux.

Technical content of the present invention: an optical add-drop multiplexer, including an optical add-drop multiplexer body, input and output ports, and add and drop ports, and wavelength division multiplexing signals are added through the optical add-drop multiplexer body Or drop switch function, characterized in that: the optical add-drop multiplexer body is a MEMS optical switch array composed of several MEMS optical switches, the MEMS optical switch is composed of a micromirror and a driving device, and the micromirror is a multilayer dielectric film The filter is composed of multiple layers of high and low refractive index material films alternately stacked. When the multiplexed wavelength hits the micromirror, only a specific wavelength is reflected, and all other wavelengths are transmitted. When the driving device turns on the MEMS optical switch When the micromirror corresponding to a specific wavelength is installed on the array, the add or drop of the specific wavelength in the wavelength division multiplexing signal can be realized.

An array of MEMS optical switches may be a plurality of MEMS optical switches arranged in a row.

The array of MEMS optical switches can be a MEMS optical switch matrix with multiple rows and columns, wherein in any row or any column, the reflection wavelength of each multilayer dielectric film filter micromirror does not repeat.

The driving device can be any MEMS optical switch driving device, such as comb-shaped cross electrode driving or micro hinge driving.

The technical effect of the present invention: because the MEMS optical switch has small size, light weight, low power consumption, high precision, fast response speed, easy large-scale integration, low insertion loss, low polarization sensitivity, format and protocol with optical signal, etc. OADM based on MEMS optical switch array has simple control, low cost, independent of signal format and protocol, compact structure, easy integration and packaging. And replace common total reflection mirror as the micromirror of MEMS optical switch with multi-layer dielectric film filter, can realize wavelength selectivity, make OADM of the present invention need not separate demultiplexer/multiplexer, have reduced insertion loss, The structure of the device is simplified, the channel isolation is high, and it is insensitive to the polarization of incident light.

Description of drawings

The present invention will be described in detail below in conjunction with the accompanying drawings.

Fig. 1 is the structural representation of optical add-drop multiplexer of the present invention;

Figure 2 is a schematic diagram of the working principle of a multilayer dielectric film filter;

Fig. 3 is the structure schematic diagram of the MEMS optical switch driven by the miniature hinge;

Fig. 4 is the schematic structural diagram of the sliding MEMS optical switch driven by the comb-shaped intersecting electrodes;

Fig. 5 is a schematic structural diagram of a multi-channel optical add-drop multiplexer based on MEMS optical switches.

Detailed ways

The OADM structure of the present invention is shown in FIG. 1 . The optical add/drop multiplexer includes: an input port, a drop port D _x (x=1, 2, 3, ..., n), an add port A _x (x = 1, 2, 3, ..., n), an output port and a MEMS optical switch array composed of n MEMS optical switches (M ₁ , M ₂ , M ₃ ,..., M _n ), wherein the MEMS optical switch adopts a two-dimensional micromirror structure, and the micro The mirror is a multi-layer dielectric film filter, which is composed of multiple layers of high and low refractive index material films alternately laminated. When the multiplexed wavelength hits the micro-mirror, only one specific wavelength is reflected by the interference effect, and the rest All wavelengths are transmitted and have wavelength selectivity.

The multi-layer dielectric film filter used in the present invention is a high reflection film for a certain wavelength, and is composed of two thin film materials with high and low refractive index alternately, and its working principle is shown in Figure 2. Assuming that the reflection wavelength is λ, properly select the thickness d ₁ and d ₂ of each layer of the multilayer dielectric film, so that the light with a free space wavelength λ reflected from each interface of the multilayer dielectric film to the front surface is in-phase coherent Enhanced, thus achieving high reflection to the lambda wavelength. The greater the difference in refractive index between the two materials, the more layers there are, and the higher the reflectivity of the multilayer dielectric film. When the multiplexed wavelengths are irradiated on the multilayer dielectric film filter, only a specific wavelength is reflected, and the rest of the wavelengths are transmitted. The multilayer dielectric film filter required to reflect one wavelength while transmitting the rest can be realized in the process. During the fabrication process, different reflection wavelengths can be controlled by adjusting the thickness of adjacent films or selecting films of different materials.

The micromirror has only two states: "ON" state and "OFF" state. When the optical switch is in the "ON" state, the micromirror is in contact with the incident light and has an effect; when it is in the "OFF" state, the micromirror has no contact with the incident light, so it has no effect. The state of the micromirror can be changed by driving the micromirror through the driving device. The driving methods of MEMS optical switches mainly include parallel plate capacitor electrostatic drive, comb electrostatic drive, electrostrictive and magnetostrictive drive, deformation memory alloy drive, optical power drive, thermal drive, etc. The driving mode of the MEMS optical switch in the present invention can be any one. Figure 3 and Figure 4 show two typical driving modes respectively. FIG. 3 is a schematic diagram of a MEMS optical switch driven by a micro-hinge. The optical switch mainly includes: a micromirror 1 , a base 2 , a slide bar 3 and a micro-hinge 4 . Driven by the slide bar 3 and the micro hinge 4 , the micromirror 1 can be lifted from the surface of the base 2 . When the driving voltage is not applied, the micromirror 1 is parallel to the surface of the base 2 and is in the "OFF" state; after the driving voltage is applied, the micromirror 1 is lifted from the surface of the base 2 and is in the "ON" state. FIG. 4 is a schematic diagram of a sliding MEMS optical switch drive device driven by comb-shaped intersecting electrodes. The optical switch mainly includes: a micromirror 1, a suspension beam 5 and a comb-shaped intersecting electrode driver 6. The micromirror 1 is fixed on the movable suspension beam 5. In the natural state, the micromirror 1 is in the "ON" state, and selectively reflects the incident light; after the comb-shaped intersecting electrode driver 6 is applied with a driving voltage, the comb-shaped intersecting electrodes generate static electricity, and the electrostatic force makes the suspension beam 5 under force. Parallel movement occurs in the direction, driving the micromirror 1 to retreat, making it in the "OFF" state and no longer reflecting light.

Referring to Figure 1, the wavelength division multiplexing signal is directly input to the array of 1×n MEMS optical switches, and the state of the MEMS optical switches ("ON" or "OFF") is controlled by the driving device to realize the add and drop of the required wavelength. The reflection wavelengths of the n micromirrors are λ ₁ , λ ₂ , λ ₃ ···λ _n in turn. One channel of wavelength division multiplexing (WDM) signal including wavelengths λ ₁ , λ ₂ , λ ₃ ···λ _n is incident on the input port, if λ _x (x=1, 2, 3,...,n) At the same time, the local signal is on the road at the wavelength of λ _x , as long as the micromirror M _x with the reflection wavelength of λ _x is controlled by the driving device to be in the "ON" state, and the other micromirrors are kept in the "OFF" state. Under the action of the M _x micromirror in the "ON" state, the λ _x wavelength to be dropped in the input WDM signal is reflected to the drop port to realize the drop, and the remaining n-1 wavelengths pass through the micromirror transparently. The mirror arrives at the output port; because the micromirror of the multilayer dielectric film filter is double-sided reflection, the local signal to be on the road is incident through the on-road port with the wavelength λ _x , and is also reflected to the output port under the action of the micromirror M _x , which is the same as The remaining n-1 signals are synthesized into a new WDM signal. By making multiple micromirrors in the "ON" state at the same time, multiple wavelengths can be added and dropped at the same time. It can be seen that as long as the state of the micromirror is controlled by the driving device, so that the micromirror corresponding to the wavelength of the add and drop is in the "ON" state, and the rest of the micromirrors are in the "OFF" state, the output wavelength of the drop port and the output port can be controlled. Realize the function of on-road and off-road. In addition, when the micromirrors in the 1×n MEMS optical switch are all in the "ON" state, the OADM of the present invention can also act as a multiplexer and a demultiplexer.

Properly arrange the MEMS optical switches described in the present invention to form a multi-row and multi-column MEMS optical switch array, which can realize the wavelength add/drop function of n WDM signals at the same time. The structure is shown in FIG. 5 . The arrangement principle of the MEMS optical switch in the MEMS optical switch array is that in any row or any column, the reflection wavelength of each multilayer dielectric film filter micromirror cannot be repeated. The arrangement we adopt is that the reflection wavelengths of the micromirrors M ₁₁ , M ₁₂ , ..., M _1n in the first row are λ ₁ , λ ₂ , ..., λ _n in turn, and the micromirrors in the other rows are the same as the first The reflection wavelengths of the row micromirrors are the same, but they need to be placed according to the cyclic shift of the first row of micromirrors. The OADM of n-way WDM signals in the present invention can be regarded as n mutually independent OADMs, each WDM signal does not interfere with each other, and the up-and-down path is completed at the same time, and the efficiency is high.

The OADM of the present invention does not require a separate demultiplexer/multiplexer, reduces insertion loss, simplifies the device structure, has high channel isolation, is insensitive to the polarization of incident light, has nothing to do with the format and protocol of the signal, and is simple to control. Low cost, compact structure, easy integration and packaging.

Claims (5)

1. An optical add-drop multiplexer, comprising an optical add-drop multiplexer body, input and output ports, and add and drop ports, characterized in that: the optical add-drop multiplexer body is composed of several MEMS optical switches MEMS optical switch array, MEMS optical switch is composed of a micromirror and a driving device. When the mirror is on, only a specific wavelength is reflected, and all other wavelengths are transmitted. When the driving device turns on the micromirror corresponding to the specific wavelength on the MEMS optical switch array, the specific wavelength in the wavelength division multiplexing signal can be added. or get off the road. 2. The optical add/drop multiplexer according to claim 1, wherein the array of MEMS optical switches is a plurality of MEMS optical switches arranged in a row. 3. The optical add-drop multiplexer according to claim 1, wherein the array of MEMS optical switches is a MEMS optical switch matrix with multiple rows and columns, wherein in any row or column, each multilayer dielectric film The reflection wavelengths of the filter micromirrors do not repeat. 4. The optical add/drop multiplexer according to claim 1, 2 or 3, characterized in that: the driving device is comb-shaped interdigitated electrode driving. 5. The optical add/drop multiplexer according to claim 1, 2 or 3, characterized in that: the driving device is a miniature hinge driving.

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