一種新型的基于馬赫-曾德干涉儀的2×2波長選擇交叉連接器模塊

1、 A Novel 2×2 Wavelength Selective Cross-Connect Module Based on Bragg Grating Mach-Zehnder Interferometer1Feng Yonghua, Luo Fengguang, Yuan JingSchool of Optoelectronic Science and Technology, Huazhong University of Science andTechnology, Wuhan (430074E-mail ：AbstractA novel 2×2 wavelength

2、 selective cross-connect (WSXC module composed of a Bragg-grating-based Mach-Zehnder interferometer (MZI, a pair of optical waveguide, a pair of 1×2 optical switches (OSWs and a pair of Y-model combiners is proposed. Multi-channel multi-wavelength selective cross-connect can be realized with th

3、e proposed 2×2 wavelength selective crossbar, together with multi-stage interconnection networks (MIN. A 2×2 four-wavelength WSXC is demonstrated by simulation to show its flexibility.Keywords: wavelength selective cross-connect (WSXC, optical switches (OSWs, Bragg grating, Mach-Zehnder In

4、terferometer (MZI, wavelength-division multiplexing (WDM.1. IntroductionGreedy demand of high speed data rate makes wavelength-division-multiplexing (WDM on the way 1, 2. Even on board level, WDM can be used to enhance the capacity of inter-chip mesh network on electro-optical printed circuit board

5、(EOPCB. Both wavelength selective cross-connect (WSXC and optical add drop multiplexer (OADM are the key components, especially for mesh optical network to reduce cost by eliminating optical-electrical-optical conversions 3. Many dynamic WSXC and OADM architectures are fabricated with optical filter

6、s, optical couplers and optical switches 4. Bragg grating based WSXC and OADM show their advantages of low channel crosstalk, uniform channel loss, high scalability and integration with silica on silicon technology 5-6. In this paper, we propose a modular WSXC with Bragg-grating-based MZIs, optical

7、waveguide, 1×2 optical switches and Y-model combiners. The proposed WXSC not only inherits the characteristics mentioned above, but also has the advantages of fully controlled wavelength selectivity.2. Architecture of Proposed WSXCThe proposed WXSC is cascaded stage by stage with element module

8、s. Each element module is composed of a Bragg-grating-based Mach-Zehnder interferometer (BG-MZI, a pair of 1×2 optical switches (OSWs and a pair of Y-model combiners, and a pair of waveguide, as Fig. 1.1This work was supported in part by the Natural Science Foundation of China under Grant No.60

9、677023 and by Hi-Tech Research and Development Program of China under Grant No. 2006AA01Z240. Fig.1. Element module of the proposed WSXCThe labels I 1, I 2, O 1 and O 2, as illustrated, have two meaning: (1 the port name of the two input ports and the two output ports; (2 the set of optical waveleng

10、th of the corresponding port. The labels K1 and K2 are used to denote both the two 1×2 OSWs and the control signal of the two 1×2 OSWs. To make a mathematical description of this element module, the following rule is assumed: K1 (K2 = 1 means optical signal in port I 1 (I 2 is guided to th

11、e Y-combiner of port O 2 (O 1 through the solid line while K1 (K2 = 0 means optical signal in port I1 (I 2 is guided into the BG-MZI by the dotted line and is denoted by12( . According to the characteristics of BG-MZI7, the ports relationship of the element module can be described as follows:m m I I

12、 I I shows the wavelength selectivity of the proposed 2×2 WSXC, which is determined by the central wavelength of the Bragg grating. The 2×2 matrix 1212K K shows the cross-connect controllability of the selected wavelength, which is accomplished by the two optical switches. The 1×2 mat

13、rix 1122(m m I I I I I I presents the remaining optical wavelength of the inputs, which is passing uncontrollably through the WSXC. The 2×2 matrix 0110indicates the outgoing direction of the remaining wavelength. Multiple-stage WSXC can be constructed with cascaded different grating wavelength

14、modules. Fig. 2 shows a 2×2 four-wavelength WSXC based on right perfect shuffle interconnection pattern. Fig.2. Architecture of the proposed WSXC with four-stage cascaded element modulesThe mathematic description of the four-stage WSXC can be given as:241112342(, , , 1001K K K K K K K K =+I I I

15、 I I I I I I I I I I I I I I I I I 21234(, , , I I (2 The equations above show the fully controllable wavelength selectivity of the proposed WSXC. The wavelengths coming from either input port can be distributed to intended output port by controlling the state of the corresponding OSWs. Note that th

16、e unit matrix of the last item of Eq.(2 means uninterested wavelength would pass through the WSXC.3. Demonstration by SimulationTo demonstrate the excellent wavelength selectivity of the proposed WXSC, we set up a simulation of four-stage WSXC as Fig. 2. In our simulation, the insertion losses of MZ

17、I, OSW and combiner are 0.5 dB, 0.5dB and 0.2 dB, respectively. The reflectivity of Bragg grating at center wavelength is about 99%. The power of CW laser of every channel is 10dBm, and is modulated by RZ modulator, which is driven by 2.5 Gb/s 2321pseudorandom binary sequence. Optical channels of wa

18、velengths 0 (193.0 THz, 1 (193.1 THz, 2 (193.2 THz, 3 (193.3 THz, 4 (193.4 THz and 5 (193.5 THz are used. The center wavelengths of the Bragg gratings labeled1, 2, 3 and4 in Fig. 2 are the same as above.We assumed the input wavelength set I 1=2, 3, 4, 5, I 2=0, 1, 2, 3 and set the control signals of

19、 the OSWs K11 K12 K13 K14 = 0101, K21 K22 K23 K24 =1010. According to Eq. (2, we could get the output wavelength set O 1 =1, 3, 5, O 2 =0, 2, 4.The optical spectrum of port I 1, I 2, O 1 and O 2 of the simulation is shown as Fig. 3 (a, (b, (c and (d, respectively. Though optical wavelengths2 and 3 a

20、ppeared in both input ports, the power of the optical wavelength 2 or 3 of the corresponding output port was the sum of that of input ports, as can be seen form the 3dB difference from other wavelengths of output ports. The wavelengths 0 and 5 were out of control in our experimental system and passe

21、d through the four-stage WSXC to their corresponding output ports O2 and O1. (c(b(a Fig. 3. Experimental results of the proposed four-stage WSXC: (a, (b, (c and (d are Spectrum diagrams of the port I 1, I 2, O 1 and O 2, respectively.Besides the fully controlled wavelength selectivity, small discrep

22、ancy of the system insertion loss between different channels is also an advantage of the proposed WSXC 6. The power loss of this four-stage WSXC is about 4 dB as indicated by the spectrum diagrams. However, compensated by optical amplifier, the power loss due to stage cascading will not limit the WS

23、XCs scalability. The crosstalk is below -20dB and can be further suppressed. 4. SummaryWe proposed a simple 2×2 WSXC with excellent wavelength selectivity. The element module is composed of a Bragg-grating-based MZI, a pair of waveguide, a pair of 1×2 OSWs and a pair of Y-model combiners.

24、The modular architecture makes the proposed WXSC prone to be integrated. If the two 1×2 OSWs are controlled by one control signal, the proposed 2×2 WSXC element module can be viewed as a 2×2 wavelength selective crossbar. Multi-channel multi-wavelength selective cross-connect can be r

25、ealized with the 2×2 wavelength selective crossbar, together with multi-stage interconnection networks (MIN. By carefully choosing the MIN, WSXC based on the 2×2 wavelength selective crossbar can only switch the interested wavelength and let other wavelength pass through.(d References 1 2

26、3 4 5 6 7 B. Mukherjee, “WDM optical communication networks: Progress and challenges,” IEEE J. Sel. Areas Commun., vol. 18, no. 10, pp. 18101824, Oct. 2000. T. Houbavlis and K.E. Zoiros, "The role of photonics technology in the implementation of future broadband telecommunications networks"

27、;, Journal of the Communications Network 2, Part 4, pp. 40-45, 2003. W. D. Zhong, J. P. R. Lacey and R. S. Tucker, “Wavelength Cross-connect for Optical Transport Networks,” J. Lightw. Technol. vol. 14, pp.16131620, 1996. G. Wilfong, B. Mikkelsen, C. Doerr, and M. Zirngibl, “WDM Cross-Connect Architectures with Reduced Complexity,” J. Lightw. Technol. vol. 17, no. 10, pp. 17321741, Oct. 1999. S. K. Liaw, K. P. Ho and S. Chi, “Multichannel add/drop and cross-connect using fibre Bragg grating and