5 GILES, c.~, MIZKAHI, v., and ERDOGAN. T.: ‘Polarization- We modulated one tcst channel with both the baseband and digital video signals using an R F combiner and an LiNbOi modu- lator (bandwidth: -1.7GHz). Thc baseband signal operated at independent phase conjugation in a reflective optical mixer’, IEEE Photonic.r Tecknol. Left., 1995, I, pp. 126-128 6 KO, K.Y., DEMOKAN. M.S., alld ‘TAM. R. Y.: ‘Transient analysis Of erbium-doped fiber anlplifiers’, IEi% ~hotol1ic.r ~echI70~. Left., 155Mbit/s (pattern length: 231 ~ 1). Usillg MPEG compressioll and QpsK modulation, NTSC “ideo could be compressed into a 3-6Mbitis digital signal and transmitted over a 6MHz SCM chan- nel, as AM-VSB CATV signals [4]. Thus, we used 10 tones (sepa- rated by 6MHz from each other) at around 1.5GHz to simulate the digital video signals. The other 14 channels were connected to thc WGR via attenuators lo simulate the insertion losses of the 1994, 6, pp, 1436-1438 Circulator + fibre (11 kin) loss (dB) Filter loss: BPFl and BPF2 (dB) Coupler loss (dB) Power (dBm) Spectrum-sliced bidirectional passive optical network for simultaneous transmission of WDM and digital broadcast video signals D.K. Jung, H. Kim, K.H. Han and Y.C. Chung A bidircctional WDM passive optical network bascd on thc spectruin-slicing tcchnique ror both broadband switched serviccs and digital broadcast video services is demonstrated. This network is capable of providing a 15SMbiUs baseband signal and 30 digital video signals to each subscriber. The upstream channels also operate at I5SMbiVs. Introduction: WDM passive optical networks (PONS) offcr many advantages, including largc capacity, nelwork security, and upgradability [I]. However, for the practical implemeutation of these networks, it is essential to develop low-cost WDM sources and use the outside plants efficiently. For this purpose, we previ- ously demonstrated a potentially cost-effective WDM PON by using spectrum-slicedWDM sources and only one waveguide grat- ing router (WGR) at the remote node (RN) for both demultiplex- ing the downstrcam channels and multiplexing the upstream channels [2]. In this Letter, we implement this network in a bidirectional configuration to enhance its cost-effecliveness. In addition, we demonstrate that this network could be used for not only broadband switched services but also digital broadcast video services without using additional optical sources or altering oul- side plant. IC0 video+data I 4 4 3.5 3.5 3.5 3.5 -20.8 at receiver 42 at EDFA 1 I RN data DDCO I DEMUXiMUX * -’“. ;A 1014111 subscriber 1 : subscriber 16 Fig. 1 Propred hidircctionul WDM PON ir.riiig specfriini-slicing tech- MOD: LiNbO, modulator, C: RF combiner, S: RF splitter Experiment: Fig. 1 shows the experimental setup to demolistrate the proposed bidirectional WDM PON. We used a spectrum- sliced fibre amplifier light source at the central office (CO), which consisted of a two-stage EDFA, a 14nm bandpass filter, and a 16 x 16 WGR. The EDFA was pumped in the counter-propagat- ing direction using a 140mW pump laser at 1.48p”. A bandpass filter (BPFl), centered at 1560nm, was used to limit the spectral rlique modulators (1 1.5dB) After transmission through lokin of conven- tioiial singleinode fibre (SMF), the multiplexed downstrcain cham nels entered port 8 of the WGR at the RN, which served as a demultiplexer. The demultiplexed channels werc then sent to the corresponding subscribers via 1 km of SMF. A pin-FET receiver (bandwidth I.7GHz) was used with a bandpass filter (BPFl) at the subscribcr’s site. This filter was used to avoid the crosstalk caused by multiplexing thc upstream signals using the same WGR. The output signal of the receiver was split, and sent to an error detector via a lowpass filter (LPF: 100MHz) and an R F spectrum analyser via a highpass filter (HPF: 700MHz) for the BER and CNR measurements, respectively. Table 1: Power budget of proposed network Dowiistream Upstream Power at transmitter (dBm) Slicing loss (dB) Router loss (dB) MOD loss (dB) 11.5 NA EDFA gain (dB) lOdB/div uustream downstream 2 i ._ LJ 5 + ._ 1530 1540 1550 1560 1570 Xz nm a Fig. 2 Meuvuwd opticul und RF .spec 0 0316 0632 0948 1264 1 580 frequency, GHz b m 11 R U Optical spcctrum of 15 downstrcam and 15 upstream chaiincls b RF spectrum of downstream channel incasured at output or pin- FET receiver width’of the ASE to be the same as the he-speclral range(FSR) of the WGR [3]. The EDF lengths of the first and second stages Results: The simultaneous use of WGRs as multiplexers and were 200 and 50m, respectively. The bandwidth and channel spac- demultiplexers, as in the proposed network, could result in serious ing of the WGR were 0.35 and O.Xnin, respectively. The lotal out- crosstalk-induced penalties due to the signals traversing in the put power of the EDFA was +17.8dBm while the output power of opposite direction [2]. We suppressed these crosstalks penalties to each channel was 4 to -I dBm. a negligible level by using two types of bandpass filter (BPFI and 308 ELECTRONICS LEPTERS 1st March 2001 Vol. 37 No. 5