DEMUX Using Concatenated Arrayed ... - GSU CS

Waveband MUX/DEMUX Using Concatenated Arrayed-Waveguide Gratings

Shoji Kakehashi (1), Hiroshi Hasegawa (1), Ken-ichi Sato (1), Osamu Moriwaki(2) 1: Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603 Japan, [email protected], {hasegawa, sato}@nuee.nagoya-u.ac.jp, 2: NTT Photonics Laboratories, [email protected] Abstract We propose a new waveband MUX/DEMUX that uses two concatenated cyclic A WGs. The device can accommodate multiple input fibers simultaneously and as a result, the device cost and size of a waveband crossconnect can be significantly reduced. WB1 WB2 Introduction ft Broadband access is being rapidly adopted (a)ContinuousWB t t t Arrangement throughout the world and as a result traffic is ... WBk WB1 WB2 continually increasing. Further traffic expansion will occur in the near future with the introduction of new (b) Dispersive WB 444 L broadband services including IP video and HDTV, Arrangement t"T[Zi which will warrant the introduction of the hierarchical x1' 12' optical path cross-connect (HOXC). Hierarchical Xk Xk+1 Xk+2 X2k 2kk+1X2k+2 Fig. 1 WB Arrangement optical paths have been shown to decrease the total Proposed Waveband Multi/Demultiplexers cost of optical cross-connects[l][2]. To realize the Continuous WB Arrangement A. HOXC one key component is the waveband 2 depicts an example of our proposed WB A Fig. multi/demultiplexer (WB MUX/DEMUX). thin-film MUX/DEMUX; it supports a total of 32 100-GHz filter has been reported that offers 8-skip-0 band spaced channels in eight bands. The MUX/DEMUX operation supporting a total of 32 channels at 100consists of two cyclic AWGs, 32x32 and 40x40, and GHz spacing[3]. Since it requires 409 layers[3], the manufacturing challenge is significant. Furthermore, it waveguides connecting them. The device can accommodate four input fibers (A-D) simultaneously, demonstrates strong non-linear dispersion at the each of which carries 32 wavelength channels. The band edges. Other band-filters based on arrayed device demultiplexes each band on each input fiber waveguide gratings (AWG) have been reported. They and outputs each band separately from 32 (8 bands realize a 17-skip-3 band with a total of 100 channels per fiber x 4 input fibers) output ports out of 40 ports. and 100-GHz spacing[4] and an 8-skip-0 band with a An example of the specific connection patterns that total of 40 channels and 100-GHz spacing[5]. The realize this function is shown in Table 1. This is made AWG band filters are susceptible to manufacturing possible utilizing the cyclic nature[6] of the AWGs; the errors that degrad adjacent crosstalk. In this paper, we present a novel WB MUX/DEMUX that uses wavelength Ai at input port #a (a=1-N) is output from concatenated cyclic AWGs. The point of the proposed output port #b (b=1-N) when i=(a+b-2)modN +1. Please note that this specific connection arrangement WB MUX/DEMUX is that it retains multi/ prevents waveguide crossing, which is advantageous demultiplexing granularity at the individual wavelength to the monolithic realization of the device. The device channel level while outputting the WBs at different feature is generalized as follows. If the number of ports. This means that conventional cyclic AWGs can be used. The salient feature of the proposed WB channels is m, and m=(# of bands per fiber, k) x (# of MUX/DEMUX is that it can accommodate multiple channels in each band, j), then AWG X is mxm and input fibers simultaneously and demultiplex each AWG Y is (m+k)x(m+k). This device can support min band to different output fibers. The arrangement of {m/k, m/j} input fibers simultaneously. two-AWG concatenation is presented; it eliminates 32X32 40X40 any waveguide crossing that would otherwise connect AWG X AWG YE the two AWGs. The arrangements that can reduce FiberAQ1 X32) 1 1 band crosstalk and maximize output port utilization (No output) 2 2 2 2 + (No output) efficiency are also demonstrated. Fiber B

(kli

32)

9

9

.

.

:3

3

0

WB8(Fiber B)

WB7(Fiber B)

Waveband Arrangement ..1 This paper describes two WB arrangements. The first 17 17 _1 (No output) FiberG(2X1-232) 25 25 one a conventional arrangement is the continuous Fiber D (Xi 32) (No output) .\ 1 arrangement shown in Fig. 1 (a). The other is our. \ proposed dispersive arrangement as explained in Fig. 3232 39 39 ~WB2(FiberA) 1(b). From the networking point of view, the WB404 WB1(FiberA) struturehas irtully o efect n nework Fig. 2 Configuration of proposed WB MUX/DEMUX that provisioning and OA&M (Operation, Administration supports four input fibers each of which carries a total of 32 and Maintenance). 10OO-GHz spaced channels in eight bands of four channels

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AWGX Xout AWGY Yin

AWGX Xout AWGY Yin

Table 1 Connection relationship of waveguides between two AWGs (Continuous WB Arrangement)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 2 3 4 5 7 8 9 10 12 13 14 15 17 18 19 20 22 23 24 25 27 28 29 30 32 33 34 35 37 38 39 40

Table 2 Connection relationship of waveguides between two AWGs (Dispersive WB Arrangement)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 1 32 31 30 29 28 27 26 9 8 7 6 5 4 3 2 17 16 15 14 13 12 11 10 25 24 23 22 21 20 16 18

B. Dispersive WB Arrangement In the dispersive WB arrangement, the WB MUX/ DEMUX is realized with two cyclic be mxm AWGs. This MUX/DEMUX can accommodate mrk input fibers in one device. One example of the connection rules of the two AWGs is shown in Table 2, when m=32 and

(a) -10 -20

-30

-30

-40

-

B -0 0

-Co

-6

, 192.5 from the continuous WB arrangement. One is that no . E connection patterns between AWG X and Y are a) -10 possible that avoid crossings. The other is that the 3 I- -30 output port usage in AWG Y can be 100%. This -40 -50 results in higher port usage than is possible with the -60 continuous WB MUX/DEMUX. 192.5

Efficiency of port utilization As explained thus far, the proposed device can ' accommodate multiple input fibers and demultiplex each band. The number of input fibers supported can be extended by increase the number of channels in each band. For example, when m=128 and 1=16, 8

194.5

193.5

k=8. This MUX/DEMUX has two major differences

Experiment The proposed device will be realized monolithically using PLC technologies, however, to confirm device feasibility we constructed a prototype by connecting two separate uniform-loss and cyclic frequency (ULCF[7]) 32x32 AWGs with 32 optical fibers. The device can support four input fibers simultaneously. Each fiber accommodates 32 100-GHz spaced channels (192.1+0.lxn THz; n=0-31) on an ITU-T grid. Each fiber carries four dispersive bands. Each band consists of eight wavelength channels. One of the important characteristics of the MUX/DEMUX is crosstalk. The proposed device allows different input fiber connection patterns. The output WB configurations from AWG Y differ according to the input fiber connection patterns, which determine the magnitude of crosstalk at each band. The crosstalk deteriorates when neighboring output ports carry the same WB from different input fibers or carry neighboring WB on the same or different input fibers. This occurs, for example, when four input fibers are connected to AWG X input ports, #1, #16, #17, and #32. The measured worst crosstalk was then 21.58dB. One of the input fiber connection patterns that minimize crosstalk is to use input ports #1, #8, #17, and #24. The measured crosstalk value of the worst channel was improved to -31.67dB. Fig. 3 shows output spectra of WB at AWG Y output port #1 (a), #10 (b), #17 (c) and #26 (d), when input optical fiber is connected to ports #1, #8, #17, and #24 respectively.

(b) -10 -20

A

195.5

(c)

192.5

193.5

-10

'

194.5

195.5

194.5

195.5

(d)

3

193.5

194.5

195.5

-40 -50 -60

192.5

193.5

Frequency (GHz) Fig. 3 Output spectra at AWG Y: output port #1 (a), #10 (b), #17 (c) and #26 (d), when input optical fiber is connected to

port, #1, #8, #17, and #24

0.6 o 0.5 O , . o au au 0.3 0.2 b

respectively.

M

___\ -i

-multipleinputfibers(cont>ins WB) --*single input fiber (dispersive WB)

N

- .- -

z

single input fiber (continuous WB)

0

32

..

96 fiber, m Number64of channels per

128

Fig. 4 Utilization efficiency of device ports and 16 input fibers can be connected to the device with the continuous and dispersive WB arrangements, respectively. Fig. 4 shows the utilization efficiency of the device ports that is defined as the ratio of number of used ports to total port number of Xir and Yout. Here, m is changed and k is set at 8. Conclusions We have proposed a new WB MUX/DEMUX that can be realized by connecting two cyclic AWGs. One of

the particular advantages of the device is that it can be shared by multiple input fibers. This can create a WB cross-connect that offers significantly lower cost and size. References 1 L. Noirie et al., ECOC 2000, vol. 3, pp. 269-270. 2 X. Cao et al., Opticom, vol. 4874, pp. 198-210, 2002. 3 G. J. Ockenfuss et al., OFC, 2002, PD FA8. C. R. Doerr et al., IEEE Photonics Technology Letters, vol. ~~~~~~~~~4 15, no. 8, 2003. 5 S. Chandrasekhar et al., ibid., vol. 17, no. 3, 2005. 6 C. Dragone et al., ibid., vol. 3, no. 1, 1991 7 K. Okamoto, lEE Electron. Lett., vol. 33, pp. 1865-1 866, 1997

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