ECOC Technical Digest © 2011 OSA
Demonstration of a Remotely Pumped Long-Reach WDM/TDM 10 Gb/s PON with Reflective User Terminals B. Schrenk1, J.A. Lazaro1, D. Klonidis2, F. Bonada1, F. Saliou3, V. Polo1, E. Lopez1, Q.T. Le3, P. Chanclou3, L. Costa4, A. Teixeira4, S. Chatzi2, I. Tomkos2, G. Tosi Beleffi5, D. Leino6, R. Soila6, S. Spirou7, G. de Valicourt8, R. Brenot8, C. Kazmierski8, and J. Prat1 1
Universitat Politecnica de Catalunya, Dept. TSC, Jordi Girona 1, 08034 Barcelona, Spain (
[email protected], +34-93-401-7179) 2 3 Athens Information Technology (AIT), 19002 Peania, Athens, Greece, Orange Labs, 22307 Lannion, France 4 5 Instituto de Telecomunicações (IT), 3810-193 Aveiro, Portugal, Italian Communication Ministry (ISCTI), 00144 Rome, Italy 6 7 8 Tellabs Oy, Espoo, Finland, Intracom S.A. Telecom Solutions, Athens, Greece, Alcatel-Thales III-V labs, 91767 Palaiseau cedex, France
Abstract: A ring+tree PON is demonstrated from a 78 km reach rural to an urban 1:128 split configuration with field-deployed fibers at >31 dB budget and RSOA or SOA/REAM at the ONU. 2011 Optical Society of America OCIS codes: (060.2330) Fiber optics communications; (060.4250) Networks; (060.4230) Multiplexing
1. Introduction Passive optical networks (PONs) are the most promising solution for optical access as they provide low capital and operating expenditures. Combined with a colorless ONU and means of WDM/TDM multiplexing, cost-effective mass deployment can be obtained [1]. Nevertheless, PONs are compromised in their reach and customer density in case of extended optical loss budgets, where optical amplification becomes indispensible. A promising solution has been recently demonstrated in a high split trunk+tree WDM/TDM network [2], however, by placing electrically powered equipment in the optical distribution network and thus without retaining its desired passiveness. 2. Long Reach Ring+Tree 10 Gb/s PON Architecture with Remotely Pumped Amplifiers Alternatively, a remotely pumped amplification scheme can be applied. The proposed hybrid PON consists of a WDM ring as resilient feeder for the remote nodes (RN) that act as interface to local spur-like TDM access networks (Fig. 1), to which a single, amplified wavelength is dropped [3]. Fig. 2a shows the transfer characteristic for such a passive OADM ring element, whose DWDM filters have a thermal drift of <1.2 pm/ºC and are thus suitable for an implementation in outside fiber plants. The required EDF pump for the RNs is in principle delivered from the OLT. As a shared infrastructure, the ring is composed by a dual fiber to avoid Rayleigh backscattering effects, as it is the case for the tree feeder. Depending on the network parameters, namely reach and tree split, the upstream transmitter at the ONUs is constituted by either a SOA/REAM or a RSOA, having a modulation bandwidth of 12 and 7.2 GHz [4,5], while a combination of SOA+PIN acts as downstream detector. The latter enables to generate a weak pump for remote EDFs in case that a wavelength-selective feedback is provided to the ONU for seeding a pump in the 1480 nm band by ASE reamplification [6]. Moreover, a more powerful pump can be provided by introducing means of multiplexing inside this seed loop (see tree splitter in Fig. 1). The distributively pumped EDF can be located either inside the tree splitter to allow higher splitting ratios (splitter type U) or at the RN (in combination with type R). For the latter, resilient operation can be maintained even in case of a very unlikely ring cut, without costly resource over-provisioning of the pump module at the OLT. Both, RN and tree splitters are solely based on passive,
CC
U
WEST
P/C
DCFR
L
1551.72
US
US
L4
λD Dummy ONU
DS
SMF
a
SOA
L2
US
DS
a
λS
L3 H
US
λS = 1560.61 nm λD = 1559.79 nm
G
SMF J I
a
M
N
L2
L3
Suburban
25
25
2
Rural
50
25
2
Urban
5
18
1
L4
1
RX
L
ONU
CR R
SOA
1480
P
DS rate
US rate
1: 64
U
SOA/REAM
10
10
1: 16
R
chip RSOA
10
10/2.5
1:128
U
TO-can RSOA
10
2.5
a
Dummy ONU
SOA
US East
E
1480
S
1 x Splitter (SPL, SPL1+SPL2) 2 x 80/20 Coupler (CS) 3 x Circulator 2 x Pump Mux (M1,M2) 6 x Pump/Signal Mux (P/C)
F
R
P
1480
P/C
Feeder Tree 2 (λD)
4 x A/D filter 200 GHz (A/D) 4 x A/D filter 100 GHz (PS,PD) 2 x 50/50 Coupler (CR) 2 x EDF (15m) 10 x Pump/Signal Mux (P/C)
Tree Splitter:
EDF
Y
Ring RN: DS
A/D
P
R
D
1 x EDF (15m) …only for
Tree 1 (λS)
U
Tree Splitter (1:M·N) with Pump Seed Loop
L4 K
type R P/C X
US TX (REM)
A
P
R
P
Loud BM-ONU
P/C A/D
D
P
EDF O
E
D
PD
DS
Tree Split & Type
C
E
20
λD L1
∆τ
A
A/D
λP
1560.20
Scenario
+
DS
REM
λP
SMF
DS
Q
RN2 SOA
PIN
50/50
Tree
SMF D
A/D
West
TX
CO
λP
R
assumed ring cut
BPF
C
K
emulated ONUs
V
Ballast ONU
Ring S
US
SOA
P S
RX
T
Ring
Pump
PIN BPF
N
λS = 1551.32 nm λD = 1550.52 nm
US
Comb
TX
M
P
M2 CS
type U
14 80 14 90
CS
SPL1
SPL
P
14 80 14 90
M2
SPL2
X
80 C P
P/C
CS
1:M·N
M1
C
CA
1:M
EDF P
Drop
EAST
DCFT
DS
RN1
Q
B Protection Switch
A λS
US
1480
P/C
1:N
CS M1
1 14 480 90
OLT
AWG
MZM
DS
L1
P
1480
λλD λDD
λ [nm]
RN (passive OADM ring element) J
I
14 14 80 90
RN1 RN2
λS
L3 H
Feeder
Ballast Ch.
G
SMF
P/C
SMF
λD λS λD λS
ONU
λComb
Fig. 1. Fully passive ring+tree PON architecture, featuring remote pumping in its network nodes and distributed pump delivered by the ONUs.
Th.12.C.3.pdf 1
7/27/2011 4:22:26 PM
1480 channel
193.4 193.45
1490 channel
-10
193.5
0
-5
-10
-15
1
A +3
■▲
B
-5
5
6
7
8
■ 1550
1
1
1
0
1
1
2
1
1
1
▲
3
2
1
■
E
F I
20.2 1
4
3
1
1
5
1
4
1
1
1
2
1
12.1
1
1
Y
■
Q
K
-20.3
1
●
4
1
1
1
6
1
7
30 25 20 15 10
7
U
■
T
▲
S
▲
▲
RN
5
16.1
R
NO P ■
7
6
●
ONU 3
V
6
5
V preamp
J
▲
RN
1
L M
▲
■
0
■
G ▲
1
▲
H
C
9
X
■
▲ 1560
■
OLT TX
0
ring fiber
1510
4
D
1
9
RN pass
-20
9
8
15.6
→ signal evolution in the PON● OLT Pump
-10 -15
8
7
ring fiber
1500
7
6
▲ 1560
■
▲
ring I/F EDF tree I/F
1490 Wavelength [nm]
3
6
5
P
feeder fiber tree splitter drop fiber ONU drop fiber tree splitter feeder fiber tree I/F EDF ring I/F
-25 1480
5
4
Signal
RN pass
1470
4
3
0
-25 -60
2
3
ring fiber
-20
2
2
booster
-40
5
0
1
1
■
28.4
F
K
Raman
-30
pump/ONU: X at splitter: 9.4 dBm Y at RN: 6.1 dBm
0
0
-20
-50
20
37.3
▲
A
30
10
■ 1550
OSNR ■
40
Pump power level [dBm]
1550.52nm
193.25 193.3 193.35 Frequency [THz]
OSNR [dB/0.1nm]
193.2
50
ring fiber
Optical pump power [dBm / 0.1nm]
0
193.15
Signal power level [dBm]
a)
193.1
Channel Drop Add 1550.52nm 1551.32nm
Channel transmission [dB]
0 -10 -20 -30 -40 -50 -60
1551.32nm
IL w/o EDF [dB]
ECOC Technical Digest © 2011 OSA
OLT
c) b) drop DS add US RX Fig. 2. a) Transmission windows of RN1. b) Distributed pump delivered by the ONUs. c) Evolution of signals and pumps along the rural PON.
simple and commercially available components (Fig. 1) though the designs might appear as complex at first glance. Two nodes at 1551.72 nm (RN1) and 1560.2 nm (RN2) were deployed, whereas RN1 was located not farther than half the ring span and RN2 was used to investigate the worst-case scenario of having a fiber cut directly at the West OLT port, meaning the farthest distance from the East OLT side. Three scenarios have been chosen, reaching from an urban with short reach and high split to a rural with long reach and low split (see table in Fig. 1). A pump of 0.7W at 1480 nm was emitted by a fiber Raman laser at the OLT along the ring to supply the RNs. For the case of having further RNs, a stronger pump or an extra pump fiber would be required. A set of 10 wavelengths is injected into the downstream ring with 3 dBm/λ (see inset in Fig. 1). While 4 signals are related with RNs and distributed to their trees, the remaining 6 channels act as ballast to account for users loading the network. DCFs were included at the OLT in some cases to investigate the impact of chirped upstream for a certain amount of residual dispersion DR. In the suburban scenario, the ONUs feature SOA/REAMs [4] for full-duplex 10 Gb/s transmission (PRBS 2311), while the distributed ONU pump reduces the net splitting loss in the tree. The loss budget of 31.2 dB corresponds to GPON class C or 10G PON Extended Class. Fig. 2b shows the chirped pumps of 9.4 dBm per pump wavelength (i.e. ONU), which result in a reduction of the splitting loss of ~14 dB and ensures an ONU input of -5 dBm. An ASE source has been included at the splitter (type U, CA) to account for noise accumulation across the M EDFs at the first 1:M stage. However, there is no additional degradation due to the already low upstream OSNR of 25.5 dB. Dummy and Ballast ONUs were included in several trees and the ring to account for potential saturation of EDF and Raman gain. The OLT receiver is composed of a dual-stage preamplifier with a short, highly linear first stage and a longer, gain-stabilised second stage. The reception filter was centered in respect to the upstream. The BER measurements at RN2 (Fig. 3a-c) indicate that dispersion management is required due to the chirped upstream. A BER of 10-10 can be reached in case of half-duplex continuous-mode (CM) upstream (DR=260ps/nm) and also for a GPON-compatible burst-mode (BM) frame and a duty cycle of 1:4, when the EAM and also the SOA section is gated. On the contrary, for a single ONU per tree an excess gain is experienced in the EDF of the splitter, next to negligible overshoots of 0.2 dB thanks to gain clamping by the downstream. With a second, 6 dB louder ONU at the second tree splitting stage that emits packets directly before the weak ONU inside the TDM frame (see inset Fig. 3a), a penalty arises; however, with a Reed-Solomon (255,239) FEC the transmission can be still maintained. The downstream (Fig. 3b) is not degraded by the BM upstream amplification in the common EDF since it arrives strong and sets the population inversion constant. No severe distortion is visible in the CM downstream envelope and a penalty of just 0.7 dB is caused at a BER of 10-10. Finally, full-duplex transmission at 10 Gb/s has been achieved with an electrical feedforward downstream cancellation, which forwards the detected downstream pattern to the upstream modulator for synchronized counter-injection [3]. The optimum downstream extinction ratio (ER) has been found with ~4 dB (Fig. 3c), for which a BER of ~10-6 below the FEC level can be obtained for full-duplex CM-down- and upstream. A long reach rural scenario that places the RNs at 50 and 75 km has been further investigated for ONUs based on a high-gain RSOA [5]. In the demonstrated resilient case, RN1 is pumped from the OLT while RN2 receives its pump from the ONUs. The modulation rates for CM down- and upstream were 10 and 10/2.5 Gb/s, respectively. The evolution for the signal and pumps is shown in Fig. 2c. RN1 at 50 km receives the OLT pump with 16 dBm, so that a strong downstream of -11.5 dBm can be provided to the ONU for a tree split of 1:16. The upstream OSNR can be maintained as high as 31.1 dB. For RN2 at 75 km, the pump from the OLT is too weak to provide the required gain for the given optical budget. However, the ONUs of one tree are able to deliver 12.7 dBm to the RN, and thus the downstream can arrive with -20.3 dBm to the ONU, which is still acceptable for the RSOA [4]. The upstream
Th.12.C.3.pdf 2
7/27/2011 4:22:27 PM
ECOC Technical Digest © 2011 OSA
then arrives with -15.6 dBm and an OSNR still >20 dB at the OLT. The BER measurements (Fig. 3d-e) indicate that downstream reception is possible at RN2 with FEC. For a lower split of 1:8, error-free operation (BER of 10-10) can be obtained, having a penalty of just 1.6 dB with the SOA+PIN receiver compared to an APD. While a 2.5 Gb/s upstream is received at 10-10 BER for RN1 even without dispersion management, Rayleigh backscattering at the drop fiber from the upstream into the weaker seed light of the RSOA require FEC for the farther RN2 (Fig. 3d). The high chirp of the RSOA dominates the performance of the 10 Gb/s upstream, for which dispersion compensation is indispensible to reach the FEC level. In case of an overcompensated link (DR<0) the BER improves due to the chirp, leaving a power margin of >10 dB for the 10 Gb/s upstream over a loss budget of 32.2 dB (78 km and a split of 1:16) at the FEC level, proving that RSOAs are promising candidates for their deployment in next-generation PONs. 3. Field Trial with Commercial Off-The-Shelf Components in an Urban PON An urban PON configuration was further evaluated with field-deployed ring fiber. With the given excess loss, the ring budget (L1+L2) was 10.2 dB, while the tree split was 1:128 with an intermediate EDF after the first 1:8 splitting stage in the tree as in the suburban scenario (splitter type U). A commercial TO-can RSOA with a small signal gain of 14 dB and a pre-equalized modulation bandwidth of 2.5 GHz was used for 2.5 Gb/s transmission. The 10 Gb/s downstream was launched with 6 dBm/λ and no DCF was placed at the OLT. With this, the upstream arrives with an OSNR of 23.7 dB. Fig. 3f shows the BER measurements at RN2, which indicate that despite patterning effects from RSOA gain dynamics, a low upstream BER can be reached over an overall ring+tree loss budget as high as 34.2 dB. 4. Conclusion A novel PON architecture with fully passive fiber plant has been demonstrated, proving reflective modulators to be feasible for high data rates (10 Gb/s) and extended loss budgets (>31dB). On top, for the first time a RSOA has been demonstrated for 10 Gb/s upstream transmission over a loss budget of 32 dB, without electronic post-processing. Acknowledgement: This work was supported by the European FP7 SARDANA, EURO-FOS and FUTON projects, and the Spanish MICINN TEC2008-01887 and FPU program. The authors want to gratefully acknowledge Keopsys for the pump supply.
5. References [1] [2] [3] [4] [5] [6]
J.H. Lee et al., “First Commercial Deployment of a Colorless Gigabit WDM/TDM Hybrid PON System [...],” JLT 28, 344, 2010. P. Ossieur et al., “A 135-km 8192-Split Carrier Distributed DWDM-TDMA PON With 2 x 32 x 10 Gb/s Capacity,” JLT 29, 463, 2011. B. Schrenk et al., “Remotely Pumped Long-Reach Hybrid PON with Wavelength Reuse in RSOA-based ONUs,” JLT 29, 635, 2011. N. Dupuis et al., “10-Gb/s AlGaInAs Colorless Remote Amplified Modulator by Selective Area Growth [...],” PTL 20, 1808, 2008. B. Schrenk et al., “Direct 10 Gb/s Modulation of a Single-Section RSOA in PONs with High Optical Budget,” PTL 22, 392, 2010. B. Schrenk et al., “Energy-Efficient Optical Access Networks Supported by a Noise-Powered Extender Box,” JSTQE 17, 480, 2011. -1
SUBURBAN
-2
Half Duplex US at 10G
CM w/o DCF DR =900ps/nm
-3
-3
Half-Duplex CM-DS at 10G
-4
Full Duplex CM-US & DS at 10G DS-ER = 6 dB
-4
40µs
SOA DR =260ps/nm
-5
-5 CM -6
single ONU at tree
-7
125µs
-8 BM
-6 with US in CM with DCF w/o DCF
-7
-9 EAM gate +SOA gate
a)
-10 -42
-38
-34 -30 -26 OLT input power [dBm]
RURAL
-2
-22
b)
-17
-15 -13 -11 ONU input power [dBm]
c)
RN1 D R =270 ps/nm
-5 10 Gb/s
-7
RN2 D R=50 ps/nm
RN1 D R =-480 ps/nm
-8
2.5 Gb/s (RN2) D R =1330ps/nm
2.5 Gb/s (RN1) D R =900ps/nm
-9 -10
RSOA -35
-32
-29
-26
-23
-20
-17
-14
optimum
-10 1
-27
4.5
2 3 4 5 6 Dow nstream ER [dB]
-25
-6 SOA+PIN
-7 -8 APD
7
6
-23 -21 -19 OLT input power [dBm]
-17
-15
-2 URBAN (Lannion, France) -3
Half Duplex CM-US at 2.5G CM-DS at 10G PRBS:
-4
7
2 -1 -5
31
2 -1
-6
DS
US
-7 -8 -9 -10
1.6 dB
TO-can RSOA
-11
-11 -38
3
-8
-5
-10
-11
US
2
-4
-9
D R =690ps/nm D R =50ps/nm
D R =270ps/nm
DS
-6
Half-Duplex CM-DS at 10G at RN2 (DR =690ps/nm)
-2
log (Downstream BER)
log (Upstream BER)
-9
-3
-4
DS
-4
ER [dB]
US
-11
-3
-6
-8
-10
Half Duplex CM-US at 10G/2.5G
2.5 Gb/s (RN2)
-2
0.7 dB
with US in BM +loud ONU (w/o DCF)
with 6dB louder ONU
-11
3 dB
-9
-10
REAM
-7
-8
-9
4.5 dB
-6
log(Up-/Downstream BER)
BM w. loud ONU
DS envelope with loud ONU
log(min. BER)
-4
-5
log(Upstream BER)
w. DCF DR =260ps/nm
log(Downstream BER)
log(Upstream BER)
-3
-23
-21
-19
-17
-44
-36
-28
-20
-12
e) ONU input power [dBm] d) f) OLT/ONU input power [dBm] OLT input power [dBm] Fig. 3. BER measurements for a-c) the suburban, d-e) the rural long-reach PON and f) the urban PON scenario with field-deployed fibers.
Th.12.C.3.pdf 3
7/27/2011 4:22:27 PM
