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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 24 — Nov. 21, 2011
  • pp: 24370–24375
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Comparison of 8 × 112 Gb/s PS-QPSK and PDM-QPSK signals over transoceanic distances

Markus Nölle, Johannes Karl Fischer, Lutz Molle, Carsten Schmidt-Langhorst, David Peckham, and Colja Schubert  »View Author Affiliations


Optics Express, Vol. 19, Issue 24, pp. 24370-24375 (2011)
http://dx.doi.org/10.1364/OE.19.024370


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Abstract

We experimentally investigate polarization-switched quadrature phase-shift keying (PS-QPSK) with a symbol rate of 37.3 GBd corresponding to a bit rate of 112 Gb/s. In a wavelength-division multiplexing (WDM) experiment with 50 GHz channel spacing, the transmission performance of PS-QPSK is compared to that of polarization-division multiplexed QPSK (PDM-QPSK) over an EDFA amplified ultra-large-effective-area fiber link. For a bit-error ratio (BER) of 3.8 × 10−3, the achieved transmission distance is 11000 km for PS-QSPK and 10000 km for PDM-QPSK.

© 2011 OSA

1. Introduction

In recent years, coherently detected PDM-QPSK emerged as a favored solution for 100G Ethernet transport over transoceanic distances [1

1. M. Salsi, H. Mardoyan, P. Tran, C. Koebele, E. Dutisseuil, G. Charlet, and S. Bigo, “155×100Gbit/s coherent PDM-QPSK transmission over 7,200km,” in Proc. 35th Eur. Conf. Opt. Commun., Sept. 2009, paper PD2.5.

-4

4. J.-X. Cai, Y. Cai, C. R. Davidson, D. G. Foursa, A. J. Lucero, O. V. Sinkin, W. W. Patterson, A. N. Pilipetskii, G. Mohs, and N. S. Bergano, “Transmission of 96×100-Gb/s Bandwidth-Constrained PDM-RZ-QPSK Channels With 300% Spectral Efficiency Over 10610 km and 400% SE Over 4370 km,” J. Lightwave Technol. 29, 491–498 (2011).

]. For WDM transmission on a 50 GHz channel grid, a reach of 9000 km has been demonstrated using pure-silica core fiber and amplification by erbium-doped fiber amplifiers (EDFA) only [3

3. M. Salsi, C. Koebele, P. Tran, H. Mardoyan, S. Bigo, and G. Charlet, “80×100-Gbit/s transmission over 9,000km using erbium-doped fibre repeaters only,” in Proc. 36th Eur. Conf. Opt. Commun., Sept. 2010, paper We.7.C.3.

]. By using narrow optical pre-filtering of the 112 Gb/s PDM-QPSK signals and a maximum a posteriori (MAP) detection algorithm, transmission over 10610 km was achieved on a 33-GHz channel grid [4

4. J.-X. Cai, Y. Cai, C. R. Davidson, D. G. Foursa, A. J. Lucero, O. V. Sinkin, W. W. Patterson, A. N. Pilipetskii, G. Mohs, and N. S. Bergano, “Transmission of 96×100-Gb/s Bandwidth-Constrained PDM-RZ-QPSK Channels With 300% Spectral Efficiency Over 10610 km and 400% SE Over 4370 km,” J. Lightwave Technol. 29, 491–498 (2011).

]. Both [3

3. M. Salsi, C. Koebele, P. Tran, H. Mardoyan, S. Bigo, and G. Charlet, “80×100-Gbit/s transmission over 9,000km using erbium-doped fibre repeaters only,” in Proc. 36th Eur. Conf. Opt. Commun., Sept. 2010, paper We.7.C.3.

] and [4

4. J.-X. Cai, Y. Cai, C. R. Davidson, D. G. Foursa, A. J. Lucero, O. V. Sinkin, W. W. Patterson, A. N. Pilipetskii, G. Mohs, and N. S. Bergano, “Transmission of 96×100-Gb/s Bandwidth-Constrained PDM-RZ-QPSK Channels With 300% Spectral Efficiency Over 10610 km and 400% SE Over 4370 km,” J. Lightwave Technol. 29, 491–498 (2011).

] used a span length of ≈50 km and EDFA-only amplification. In [2

2. E. Torrengo, R. Cigliutti, G. Bosco, and G. Gavioli, A. Alaimo A. Carena, V. Curri, F. Forghieri, S. Piciaccia, M. Belmonte, A. Brinciotti, A. L. Porta, S. Abrate, and P. Poggiolini, “Transoceanic PM-QPSK Terabit superchannel transmission experiments at Baud-rate subcarrier spacing,” in Proc. 36th Eur. Conf. Opt. Commun., Sept. 2010, paper We.7.C.2.

], a 33 GHz channel grid was achieved using optical Nyquist filtering. While [3

3. M. Salsi, C. Koebele, P. Tran, H. Mardoyan, S. Bigo, and G. Charlet, “80×100-Gbit/s transmission over 9,000km using erbium-doped fibre repeaters only,” in Proc. 36th Eur. Conf. Opt. Commun., Sept. 2010, paper We.7.C.3.

] and [4

4. J.-X. Cai, Y. Cai, C. R. Davidson, D. G. Foursa, A. J. Lucero, O. V. Sinkin, W. W. Patterson, A. N. Pilipetskii, G. Mohs, and N. S. Bergano, “Transmission of 96×100-Gb/s Bandwidth-Constrained PDM-RZ-QPSK Channels With 300% Spectral Efficiency Over 10610 km and 400% SE Over 4370 km,” J. Lightwave Technol. 29, 491–498 (2011).

] assumed 7% overhead for a hard-decision forward error correction (FEC), 20% was assumed in [2

2. E. Torrengo, R. Cigliutti, G. Bosco, and G. Gavioli, A. Alaimo A. Carena, V. Curri, F. Forghieri, S. Piciaccia, M. Belmonte, A. Brinciotti, A. L. Porta, S. Abrate, and P. Poggiolini, “Transoceanic PM-QPSK Terabit superchannel transmission experiments at Baud-rate subcarrier spacing,” in Proc. 36th Eur. Conf. Opt. Commun., Sept. 2010, paper We.7.C.2.

], resulting in a BER of 10−2 at the FEC limit. This enabled a transmission reach of 10000 km.

Two years ago, Karlsson [5

5. M. Karlsson and E. Agrell, “Which is the most power-efficient modulation format in optical links?” Opt. Express 17(13), 10814–10819 (2009).

] and Agrell [6

6. E. Agrell and M. Karlsson, “Power efficient modulation formats in coherent transmission systems,” J. Lightwave Technol. 27(22), 5115–5126 (2009).

] as well as Bülow [7

7. H. Bülow, “Polarization QAM (POL-QAM) for coherent detection schemes,” in Proc. Opt. Fiber Commun. Conf., Mar. 2009, paper OWG2.

] explored the optimal placement of constellation points in the four-dimensional (4-D) signal space spanned by the electric field components in optical single-mode fibers. A numerical optimization using sphere packing in 4-D space identified PS-QPSK as the most power efficient 4-D modulation format [5

5. M. Karlsson and E. Agrell, “Which is the most power-efficient modulation format in optical links?” Opt. Express 17(13), 10814–10819 (2009).

]. Compared to PDM-QPSK at a BER of 10−3, it offers approximately 1 dB sensitivity improvement for the same bit rate [6

6. E. Agrell and M. Karlsson, “Power efficient modulation formats in coherent transmission systems,” J. Lightwave Technol. 27(22), 5115–5126 (2009).

].

In [12

12. J. K. Fischer and L. Molle, M, Nölle, D.-D. Groß, and C. Schubert, “Experimental Investigation of 28-GBd Polarization-Switched Quadrature Phase-Shift Keying Signals,“ in Proc. 37th Eur. Conf. Opt. Commun., Sept. 2011, paper Mo.2.B.1.

], we report on the generation of 28 GBd (84 Gb/s) PS-QPSK signals using an integrated dual-polarization (DP) I/Q-modulator and assessed the single-channel transmission performance over transoceanic distances up to 12500 km. In this contribution, we increase the symbol rate to 37.3 GBd to generate 112 Gb/s PS-QPSK signals. The performance of these signals is evaluated in back-to-back and WDM transmission using a fiber loop with ultra-large effective area fiber (ULAF) spans with up to 15000 km transmission distance. Furthermore, the performance is compared to that of PDM-QPSK signals at the same bit rate of 112 Gb/s.

2. Experimental setup

The schematic of our experimental setup is shown in Fig. 1
Fig. 1 (a) Experimental setup of 112 Gb/s PS-QPSK and DP-QPSK eight-channel WDM transmitter, circulating transmission loop and coherent receiver. (b) detailed schematic of the transmitter setup, (c) PolSK modulator and Pol-MUX emulator used for the neighboring channels. ECL: external cavity laser, DFF: D-flip-flop, Pol-Ctrl: polarization controller, MZM: Mach-Zehnder modulator, BPF: optical band-pass filter, VOA: variable optical attenuator.
. We used eight tunable lasers (line width ~100 kHz) as light sources to generate 50 GHz spaced WDM channels using twomodulator rails for the odd and even channels. The upper rail consists of a single integrated DP-I/Q-modulator (Fujitsu FTM7977HQA), which can create both PDM-QPSK and PS-QPSK signals by simply changing its driving signal sequences d1d4. To create 112 Gb/s PDM-QPSK, four 28 Gb/s pseudo-random binary sequences (PRBS) of length 215-1 are generated from a four-channel bit pattern generator (BPG), with d2, d3 and d4 mutually delayed relative to d1 by 16383, 8191 and 24574 bits, respectively. For the generation of 112 Gb/s PS-QPSK, d4 needs to be coded as XOR combination of d1, d2 and d3 [5

5. M. Karlsson and E. Agrell, “Which is the most power-efficient modulation format in optical links?” Opt. Express 17(13), 10814–10819 (2009).

]. Furthermore, the bit rate of the driving signals needs to be increased to 37.3 Gb/s. Since this bit rate is above the maximum specified bit rate of 32 Gb/s of the employed BPG (SHF 12103A), it cannot generate freely programmable data sequences to accomplish the XOR operation. However, it can still generate four independent 37.3 Gb/s PRBS (after custom calibration by the manufacturer). We utilized a special property of PRBS to mimic the XOR coding required for PS-QPSK. It was pointed out in [13

13. M. Wrigth, “Comments on ‘Aspects of MLS measuring systems,’,” J. Audio Eng. Soc. 43, 48–49 (1995).

], that a PRBS preserves its structure when XOR-ed with a circularly delayed (by i bits) replica of itself, i.e. if d(n) is a PRBS of length L, then d(n) ⊕ d(n-i) = d(n-k) for i0, m⋅L and k ≠ 0, i with i, k, m and n being integers and ⊕ indicating XOR-operation. The resulting shift k can be found numerically by evaluating the cross correlation of d(n) and d(n-k). Using the delays for d1d3 as before and applying this rule twice to d4 = d1d2d3 results in a required shift of 20739 bits for d4 relative to d1. The resulting eye diagrams generated with the DP-I/Q modulator are shown in Fig. 2 (b)
Fig. 2 (a) Spectrum of 8 × 112 Gb/s PS-QPSK after 50 GHz ILV (red) and after 10000 km transmission (blue), (b) eye diagram of PS-QPSK before (top) and after (bottom) 50 GHz ILV, (c) received back-to-back constellation for 112 Gb/s PS-QPSK, 40 dB OSNR (d) –(f) spectra, eye diagram and constellation for 112 Gb/s PDM-QPSK.
for PS-QPSK and Fig. 2 (e) for PDM-QPSK.

The lower modulator rail consists of a single-polarization I/Q modulator (Fujitsu FTM7961EX) driven by d¯1 and d¯2 in order to generate a single-polarization QPSK signal. For the generation of 112 Gb/s PS-QPSK, the I/Q modulator is followed by a polarization-shift keying (PolSK) stage as proposed in [14

14. M. Sjödin, P. Johannisson, H. Wymeersch, P. A. Andrekson, and M. Karlsson, “Comparison of polarization-switched QPSK and polarization-multiplexed QPSK at 30 Gbit/s,” Opt. Express 19(8), 7839–7846 (2011).

]. In the PolSK stage, the 37.3 GBd QPSK signal is split by a polarization beam splitter (PBS) and amplitude-modulated by two inversely driven (d4 andd¯4) Mach-Zehnder modulators (Oclaro SD40). The signals are subsequently recombined in a polarization beam combiner (PBC). For generation of 112 Gb/s PDM-QPSK, the BPG was clocked at 28 GBd and the PolSK stage was replaced by a polarization-multiplex (Pol-MUX) emulator, consisting of a PBS at its input, a passive delay stage with a relative delay of 33 ns (924 symbols) for decorrelation and a PBC to recombine the polarization tributaries.

Because of its better PS-QPSK performance, we used the upper DP-I/Q modulator rail throughout the measurements to modulate the even or odd channel group under test, whereas the lower rail was used for the complementary odd or even neighbor channels, respectively.

After boosting by EDFAs, the two modulated optical combs are combined with a programmable optical interleaver filter (ILV) onto the 50 GHz ITU grid and sent to the 250 km recirculating fiber loop. The loop timing is determined by two acousto-optical switches (AOS) driven by complementary control pulses. The EDFA-amplified transmission loop consists of two 80 km spans and one 90 km span of ULAF (kindly provided by OFS), with chromatic dispersion (CD) of 20 ps/(km∙nm), dispersion slope of 0.07 ps/(km∙nm2), attenuation of 0.184 dB/km, and an effective area of 126 µm2 (parameters averaged over fiber segments). The fiber launch powers and unity loop gain are set by variable optical attenuators included in the EDFAs. A 5 nm optical band pass filter and a programmable gain equalization filter (GEQ) were used to suppress noise accumulation outside the signal band and to correct wavelength dependent EDFA gain. We also inserted a second AOS inside the loop (not shown in setup) to compensate for the Doppler frequency shift induced by the other loop-internal AOS. Optical WDM spectra after the transmitter and after transmission over 10000 km are shown in Fig. 2 (a) and (d).

At the receiver, the signal can be artificially noise-loaded for back-to-back performance characterization. Subsequently, the channel under test is selected by a 0.4 nm optical band pass filter before being fed into a polarization-diversity optical 90°-hybrid. The local oscillator (LO) laser is an ECL with ~100 kHz line width. After detection by four balanced photo-detectors (BD) the signals are digitized by a real-time oscilloscope (Tektronix DPO72004) with 20 GHz bandwidth and 50 GSa/s sampling rate. Digital signal processing is performed offline and includes corrections of optical frontend imbalances, CD and residual frequency offset. An adaptive 2 × 2 MIMO equalizer separates the signal polarizations and compensates for residual CD, PMD and laser phase noise. The filter coefficients are updated by a modified constant modulus algorithm (CMA) as proposed in [15

15. D. S. Millar and S. J. Savory, “Blind adaptive equalization of polarization-switched QPSK modulation,” Opt. Express 19(9), 8533–8538 (2011).

]. After pre-convergence is obtained, the equalizer is switched to decision-directed mode. The equalizer feedback criterion as well as the symbol decision is based on minimum Euclidean distance in 4-D space. Finally, after symbol de-mapping and synchronization, bit errors are counted. The received constellation diagrams for maximum OSNR are shown in Fig. 2 (c) and (f) for PS-QPSK and PDM-QPSK respectively.

3. Results and discussion

The measured back-to-back BER as a function of OSNR (for 0.1 nm noise bandwidth) is shown in Fig. 3 (a)
Fig. 3 (a) back-to back performance for PS-QPSK and PDM-QPSK in a single-channel and WDM scenario: solid lines indicate theoretical limits and curves with symbols are measured values, (b) and (c) Plots of the received phase planes for PS-QPSK and PDM-QPSK, respectively, both for a BER of 10−3.
. Solid lines indicate the theoretical noise-limited BER derived for PS-QPSK in [6

6. E. Agrell and M. Karlsson, “Power efficient modulation formats in coherent transmission systems,” J. Lightwave Technol. 27(22), 5115–5126 (2009).

] and for PDM-QPSK in [16

16. F. Xiong, “Digital Modulation Techniques,” Artech House Inc, 2006.

]. For a BER of 10−3, the measured required OSNR for PS-QPSK is ≈13.5 dB, while it is ≈13.9 dB for PDM-QPSK, resulting in 0.4 dB sensitivity advantage of PS-QPSK. This is in contrast to the theoretically predicted difference of about 1 dB. The reduced sensitivity advantage for PS-QPSK is due to the higher implementation penalty (≈1.2 dB at a BER of 10−3) compared to PDM-QPSK (≈0.6 dB). Comparing single-channel and WDM results in Fig. 3, no penalty due to crosstalk is observed. Therefore, we attribute the higher implementation penalty to the increased symbol rate (by a factor of 4/3) for PS-QPSK, where bandwidth limitations of the electrical and electro-optical components are already more pronounced. The sensitivity advantage of PS-QPSK decreases to 0.3 dB near the FEC limit of 3.8∙10−3. Figure 3 (b) and (c) show plots of the phase plane of X- and Y-polarizations of the received PS-QPSK and PDM-QPSK signals at a BER of 10−3. Due to the higher symbol distances, PS-QPSK can tolerate more noise, resulting in enlarged constellation points, while achieving the same BER.

In Fig. 4 (a)
Fig. 4 (a) BER vs. fiber launch power per channel for various transmission lengths, blue curves show PS-QPSK, red curves show PDM-QPSK, (b) BER vs. transmission distance (optimized launch power for every distance).
, the BER versus fiber launch power per channel for one channel at a wavelength of 1550.92 nm after WDM transmission is shown over various numbers of loop roundtrips. Blue symbols indicate PS-QPSK measurements, while red symbols denote PDM-QPSK. For launch powers below −1 dBm per channel, i.e. in the linear regime, the performance of both modulation formats is similar, which was expected considering the similar back-to-back performance. At higher launch powers, nonlinear effects start to limit the transmission performance. In Fig. 4 (a) it is seen that the optimum launch power is between 1 dB and 2 dB higher for 112-Gb/s PS-QPSK, depending on the transmission length, which indicates a higher nonlinear tolerance of this format compared to 112-Gb/s PDM-QPSK. A similar behavior was observed for example in numerical simulations [8

8. P. Poggiolini, G. Bosco, A. Carena, V. Curri, and F. Forghieri, “Performance evaluation of coherent WDM PS-QPSK (HEXA) accounting for non-linear fiber propagation effects,” Opt. Express 18(11), 11360–11371 (2010).

,9

9. P. Serena, A. Vannucci, and A. Bononi, “The performance of polarization switched-QPSK (PS-QPSK) in dispersion managed WDM transmission,” in Proc. 36th Eur. Conf. Opt. Commun., Sept. 2010, paper Th.10.E.2.

] and experimental investigations [11

11. L. E. Nelson, X. Zhou, N. Mac Suibhne, A. D. Ellis, and P. Magill, “Experimental comparison of coherent polarization-switched QPSK to polarization-multiplexed QPSK for 10 × 100 km WDM transmission,” Opt. Express 19(11), 10849–10856 (2011).

] of a SSMF link. However, this may depend on the actual system configuration, since measurements at 42.9 Gb/s over 80 km SSMF spans [10

10. D. S. Millar, D. Lavery, S. Makovejs, C. Behrens, B. C. Thomsen, P. Bayvel, and S. J. Savory, “Generation and long-haul transmission of polarization-switched QPSK at 42.9 Gb/s,” Opt. Express 19(10), 9296–9302 (2011).

] did not indicate such a nonlinear advantage for PS-QPSK.

In Fig. 4 (b), the BER as a function of distance is shown for optimum launch powers at each distance. Assuming a FEC limit of 3.8∙10−3 as upper BER limit, the achievable transmission distances are ≈12000 km and ≈11000 km for PS-QPSK and PDM-QPSK, respectively. To ensure that all eight WDM channels are well below the FEC threshold, the BER of the individual channels were measured at the optimum channel launch power ( + 1 dBm and −1 dBm) after 11000 km and 10000 km transmission for PS-QPSK and PDM-QPSK, respectively. The measured BER as well as the received OSNR for all WDM channels are shown in Fig. 5 (a) and (b)
Fig. 5 BER and OSNR vs. measured channel index (shortest wavelength: 1549.715 nm, longest wavelength: 1552.524 nm), blue circles indicate BER and red triangles denote OSNR. (a) PS-QPSK for + 1 dBm channel launch power after 11000 km, (b) PDM-QPSK for −1 dBm channel launch power after 10000 km transmission.
.

4. Conclusion

In this paper, we present the experimental generation and ultra-long-haul transmission of 8 × 112-Gb/s PS-QPSK on a 50 GHz channel grid over up to 11000 km ULAF with EDFA amplification. We also compare PS-QPSK to PDM-QPSK at the same bit rate. Regarding the noise-limited performance, the theoretically predicted sensitivity improvement for PS-QPSK at a BER of 3.8∙10−3 is 0.8 dB whereas we measured only 0.3 dB improvement. We attribute this to the required higher symbol rate of PS-QPSK and the therefore associated higher implementation penalty due to bandwidth constraints of our available components.

Ultra-long-haul transmission results ≥10000 km reveal a higher optimum channel power for PS-QPSK modulation, denoting its higher nonlinear tolerance and, resulting from that, an increased transmission reach by ≈10%.

Acknowledgments

We thank J. Schunke and E. Hansen from SHF Communication Technologies AG, Berlin, for custom calibration of our pattern generator beyond its specified speed limit.

References and links

1.

M. Salsi, H. Mardoyan, P. Tran, C. Koebele, E. Dutisseuil, G. Charlet, and S. Bigo, “155×100Gbit/s coherent PDM-QPSK transmission over 7,200km,” in Proc. 35th Eur. Conf. Opt. Commun., Sept. 2009, paper PD2.5.

2.

E. Torrengo, R. Cigliutti, G. Bosco, and G. Gavioli, A. Alaimo A. Carena, V. Curri, F. Forghieri, S. Piciaccia, M. Belmonte, A. Brinciotti, A. L. Porta, S. Abrate, and P. Poggiolini, “Transoceanic PM-QPSK Terabit superchannel transmission experiments at Baud-rate subcarrier spacing,” in Proc. 36th Eur. Conf. Opt. Commun., Sept. 2010, paper We.7.C.2.

3.

M. Salsi, C. Koebele, P. Tran, H. Mardoyan, S. Bigo, and G. Charlet, “80×100-Gbit/s transmission over 9,000km using erbium-doped fibre repeaters only,” in Proc. 36th Eur. Conf. Opt. Commun., Sept. 2010, paper We.7.C.3.

4.

J.-X. Cai, Y. Cai, C. R. Davidson, D. G. Foursa, A. J. Lucero, O. V. Sinkin, W. W. Patterson, A. N. Pilipetskii, G. Mohs, and N. S. Bergano, “Transmission of 96×100-Gb/s Bandwidth-Constrained PDM-RZ-QPSK Channels With 300% Spectral Efficiency Over 10610 km and 400% SE Over 4370 km,” J. Lightwave Technol. 29, 491–498 (2011).

5.

M. Karlsson and E. Agrell, “Which is the most power-efficient modulation format in optical links?” Opt. Express 17(13), 10814–10819 (2009).

6.

E. Agrell and M. Karlsson, “Power efficient modulation formats in coherent transmission systems,” J. Lightwave Technol. 27(22), 5115–5126 (2009).

7.

H. Bülow, “Polarization QAM (POL-QAM) for coherent detection schemes,” in Proc. Opt. Fiber Commun. Conf., Mar. 2009, paper OWG2.

8.

P. Poggiolini, G. Bosco, A. Carena, V. Curri, and F. Forghieri, “Performance evaluation of coherent WDM PS-QPSK (HEXA) accounting for non-linear fiber propagation effects,” Opt. Express 18(11), 11360–11371 (2010).

9.

P. Serena, A. Vannucci, and A. Bononi, “The performance of polarization switched-QPSK (PS-QPSK) in dispersion managed WDM transmission,” in Proc. 36th Eur. Conf. Opt. Commun., Sept. 2010, paper Th.10.E.2.

10.

D. S. Millar, D. Lavery, S. Makovejs, C. Behrens, B. C. Thomsen, P. Bayvel, and S. J. Savory, “Generation and long-haul transmission of polarization-switched QPSK at 42.9 Gb/s,” Opt. Express 19(10), 9296–9302 (2011).

11.

L. E. Nelson, X. Zhou, N. Mac Suibhne, A. D. Ellis, and P. Magill, “Experimental comparison of coherent polarization-switched QPSK to polarization-multiplexed QPSK for 10 × 100 km WDM transmission,” Opt. Express 19(11), 10849–10856 (2011).

12.

J. K. Fischer and L. Molle, M, Nölle, D.-D. Groß, and C. Schubert, “Experimental Investigation of 28-GBd Polarization-Switched Quadrature Phase-Shift Keying Signals,“ in Proc. 37th Eur. Conf. Opt. Commun., Sept. 2011, paper Mo.2.B.1.

13.

M. Wrigth, “Comments on ‘Aspects of MLS measuring systems,’,” J. Audio Eng. Soc. 43, 48–49 (1995).

14.

M. Sjödin, P. Johannisson, H. Wymeersch, P. A. Andrekson, and M. Karlsson, “Comparison of polarization-switched QPSK and polarization-multiplexed QPSK at 30 Gbit/s,” Opt. Express 19(8), 7839–7846 (2011).

15.

D. S. Millar and S. J. Savory, “Blind adaptive equalization of polarization-switched QPSK modulation,” Opt. Express 19(9), 8533–8538 (2011).

16.

F. Xiong, “Digital Modulation Techniques,” Artech House Inc, 2006.

OCIS Codes
(060.1660) Fiber optics and optical communications : Coherent communications
(060.2330) Fiber optics and optical communications : Fiber optics communications
(060.2360) Fiber optics and optical communications : Fiber optics links and subsystems
(060.4080) Fiber optics and optical communications : Modulation

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: September 22, 2011
Revised Manuscript: October 24, 2011
Manuscript Accepted: October 29, 2011
Published: November 14, 2011

Citation
Markus Nölle, Johannes Karl Fischer, Lutz Molle, Carsten Schmidt-Langhorst, David Peckham, and Colja Schubert, "Comparison of 8 × 112 Gb/s PS-QPSK and PDM-QPSK signals over transoceanic distances," Opt. Express 19, 24370-24375 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-24-24370


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References

  1. M. Salsi, H. Mardoyan, P. Tran, C. Koebele, E. Dutisseuil, G. Charlet, and S. Bigo, “155×100Gbit/s coherent PDM-QPSK transmission over 7,200km,” in Proc. 35th Eur. Conf. Opt. Commun., Sept. 2009, paper PD2.5.
  2. E. Torrengo, R. Cigliutti, G. Bosco, and G. Gavioli, A. Alaimo A. Carena, V. Curri, F. Forghieri, S. Piciaccia, M. Belmonte, A. Brinciotti, A. L. Porta, S. Abrate, and P. Poggiolini, “Transoceanic PM-QPSK Terabit superchannel transmission experiments at Baud-rate subcarrier spacing,” in Proc. 36th Eur. Conf. Opt. Commun., Sept. 2010, paper We.7.C.2.
  3. M. Salsi, C. Koebele, P. Tran, H. Mardoyan, S. Bigo, and G. Charlet, “80×100-Gbit/s transmission over 9,000km using erbium-doped fibre repeaters only,” in Proc. 36th Eur. Conf. Opt. Commun., Sept. 2010, paper We.7.C.3.
  4. J.-X. Cai, Y. Cai, C. R. Davidson, D. G. Foursa, A. J. Lucero, O. V. Sinkin, W. W. Patterson, A. N. Pilipetskii, G. Mohs, and N. S. Bergano, “Transmission of 96×100-Gb/s Bandwidth-Constrained PDM-RZ-QPSK Channels With 300% Spectral Efficiency Over 10610 km and 400% SE Over 4370 km,” J. Lightwave Technol. 29, 491–498 (2011).
  5. M. Karlsson and E. Agrell, “Which is the most power-efficient modulation format in optical links?” Opt. Express 17(13), 10814–10819 (2009).
  6. E. Agrell and M. Karlsson, “Power efficient modulation formats in coherent transmission systems,” J. Lightwave Technol. 27(22), 5115–5126 (2009).
  7. H. Bülow, “Polarization QAM (POL-QAM) for coherent detection schemes,” in Proc. Opt. Fiber Commun. Conf., Mar. 2009, paper OWG2.
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