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128X128 3D-MEMS optical switch module with simultaneous optical paths


128X128 3D-MEMS optical switch module with simultaneous optical paths connection for optical cross-connect systems
M. Mizukami, J. Yamaguchi, N. Nemoto, Y. Kawajiri, H. Hirata S. Uchiyam

a, M. Makihara, T. Sakata, N. Shimoyama, H. Ishii and F. Shimokawa
NTT Microsystem Integration Laboratories, Nippon Telegraph and Telephone Corporation 3-1 Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198, Japan

Abstract: A 128 X128 3D-MEMS optical switch module has been developed. A prototype switch module enables the simultaneous switching of all optical paths. The insertion loss is less than 4.8 dB and 2.6 dB on average. Regarding environmental characteristics, we confirmed that the module operates flawlessly when temperature in the installation room changes from -5 to 50 °C. We also confirmed that the switching module satisfies the Telcordia GR-63 office vibration test and the CISPR 22 class A test for EMC. The results confirm that the module is suitable for practical use in the optical cross-connect systems. Keywords: Optical MEMS, Optical switch, Cross-connect

Optical beam Input port

Two-axis MEMS tilt mirror array

Output port

Two-axis MEMS tilt mirror array

Optical f iber collimator array

Figure 1: Configuration of a 3D MEMS optical switch fabric.

Introduction With the rapid progress of broadband Internet services, optical communications network have been extended to the office and home. There is a possibility that optical cross-connect (OXC) switches will be widely used in not only the core network but also in metro or access networks. Optical MEMS are promising for application in many optical components. Three-dimensional (3D) MEMS optical switches are attracting great interest as a large-scale all-optical switching fabric because of lower cost, compactness, and high optical performance. A MEMS optical switch provides many advantages, such as low insertion loss, low crosstalk (XT), high port number, and low polarization dependence loss. Several MEMS switches has been reported [1-2]. These switches offer a 100-200 channel scale, but the number of ports that can be simultaneous connected is not described. We have developed a 128 X 128 3D MEMS optical switch module for an OXC system. This switch module enables the simultaneous switching of all ports. Here, we describe the configuration of the module and show evaluation results for a prototype. 2. Configuration The basic configuration of a 3D MEMS optical switch fabric [3] using free-space optical interconnection is shown in Fig.1. The fabric consists of a two-axis MEMS tilt mirror array and an optical fiber collimator array. Optical beams from input ports are collimated by the collimator array and reflected by the two-axis MEMS tilt array. Connection between any input port and any output port can be achieved by controlling the tilt angle of each mirror. Figure 2 shows a photograph of the switch fabric components. High-density packaging of

MEMS mirror array

MEMS mirror

Optical fiber collimator array

Figure 2: Photograph of a switch fabric components.
CPU Command board board Control Power board module Optical I/O Interface(128X128)

355 mm

Figure 3: Photograph of the prototype optical switch module

9781-4244-3856-3/09/$25.00 ?2009 IEEE

the MEMS mirror array and optical collimator array was achieved. Figure 3 shows a photograph of the prototype optical switch module. The module consists of a circuit board for controlling the MEMS mirrors, power module, optical I/O interface, and CPU board. A compact switch was achieved by high-density mounting of each circuit board and highdensity packaging of the switch fabric. Because 8MPO connectors were used for the optical I/O interface, further compactness of the module became possible. The module is 436(W) X 350 (D) X 355 (H) mm in size and can be accommodated in a 19-inch rack. Figure 4 shows the configuration of the control circuit module. This module consists of control software to connect optical paths, control circuit hardware to drive the MEMS mirrors and monitor the optical power, and command and control boards. Decentralized processing with a FPGA for the control board and command board enables simultaneous switching of multiple optical paths 3. Evaluation results We first measured the insertion loss of the prototype, which is the main characteristic for assessing the performance of an optical switch. As shown in Fig. 5, the insertion loss is less than 4.8 dB and 2.6 dB on average, includes that of the internal 8MPO connector at 2 connection points. Figure 6 shows the experimental result of switching time measurement when 128 optical paths were connected. The average of switching time was 57ms. It was confirmed that simultaneous switching of all 128 ports can be performed. The prototype switch module performance is summarized in Table 1. Static XT of the module is less than -50 dB and dynamic crosstalk is less than -41 dB. The connection repeatability is less than 0.5 dB. These values are good enough for practical use. Regarding environmental characteristics, we confirmed that the module operates flawlessly when temperature in the installation room changes from -5 to 50 °C. We also confirmed that the switching module satisfies the Telcordia GR-63 office vibration test and the CISPR 22 class A test for EMC. 4. Conclusion We have developed a 3D MEMS optical switch module that can cross-connect 128 input and 128 output ports. The module can be installed in a 19-inch rack due to its high-density packaging. The average insertion loss is 2.6 dB and the average switching time is 57 milliseconds. Simultaneous switching for all 128 ports can be achieved. The evaluation results confirm that the 3D MEMS optical switch module is suitable for practical use.
5. References [1]  D.J. Bishop, C. R. Giles, and G. P. Austin: "The Lucent Lambda-Router: MEMS technology of the future here today", IEEE Comm. Mag., Vol. 40 No. 3, pp. 75-79, 2002 R. Ryf: “Optical MEMS in optical networks”, Proc. Of ECOC 2002, Copenhagen, Vol.1, pp. 1-32, 2002 J. Yamaguchi, T. Sakata, N. Shimoyama, H. Ishii, F. Simokawa, T. Yamamoto: "High-yield Fabrication Methods for MEMS Tilt Mirror Array for Optical Switch”", NTT Technical Review, Vol. 5, No. 10, pp. 1-6, 2007

Control software

Control circuit module hardware Control board CPU board Command board CPU FPGA Input mirror CPU FPGA Output mirror CPU FPGA

Optical path connection Peak search Optical power stabilization

OS

Input mirror array Drive circuit Test of element ? Maintenance? Input light Power monitor circuit D/A+AMP

Output mirror array Drive circuit D/A+AMP

GUI

Core module Power monitor circuit MPO

Communication line

MPO

Output light

Figure 4: Configuration of the control circuit module.
???? ???

Number of ??? connection path

??? ??? ??? ??? ??? ??? ??? ??? ? ? ??? ? ???

N=16512 (129x128 matrix? Avg.=2.6dB V=0.7dB

? ??? ? ??? ? ??????? Insertion loss [dB]

???

?

Figure 5 : Insertion loss distribution.
Peak Search

? 10 ??? 0 ??? -10 -20 ??? -30 ??? -40 ??? -50 ??? -60 ??? ? ????

Optical power [dBm] ????????

Switching time 57ms ? Av.?

Maximum Optical power

Path connection start ??? (Simultaneous switching) ??????????

??? Time [s] ?????

????

???

Figure 6: Simultaneous switching of all connection paths.

Table 1: Performance of the prototype switch module
Port capacity Insertion loss Switching time Simultaneous switching Repeatability of connection Interference with another connecting path Crosstalk (static) Crosstalk (Dynamic) 128 X 128 2.6 dB (Av.) <57 ms 128 <0.5 dB <0.5 dB <-50 dB <-41 dB

[2] [3]

9781-4244-3856-3/09/$25.00 ?2009 IEEE


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