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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 9 — May. 5, 2014
  • pp: 10477–10486
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Optical signal to noise ratio improvement through unbalanced noise beating in phase-sensitive parametric amplifiers

R. Malik, A. Kumpera, S.L.I. Olsson, P.A. Andrekson, and M. Karlsson  »View Author Affiliations


Optics Express, Vol. 22, Issue 9, pp. 10477-10486 (2014)
http://dx.doi.org/10.1364/OE.22.010477


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Abstract

We investigate the beating of signal and idler waves, which have imbalanced signal to noise ratios, in a phase-sensitive parametric amplifier. Imbalanced signal to noise ratios are achieved in two ways; first by imbalanced noise loading; second by varying idler to signal input power ratio. In the case of imbalanced noise loading the phase-sensitive amplifier improved the signal to noise ratio from 3 to 6 dB, and in the case of varying idler to signal input power ratio, the signal to noise ratio improved from 3 to in excess of 20 dB.

© 2014 Optical Society of America

1. Introduction

2. Theory

3. Experiment and results

Fig. 1 Experimental set-up for noise loading. WS: Waveshaper; EDFA: erbium-doped fiber amplifier; OSA: optical spectrum analyzer; Pol: polarizer; FOPA: fiber optical parametric amplifier; PLL: phase locked loop; OSA: optical spectrum analyzer.
Figure 1 shows the experimental set-up. The pump seed was provided by a fixed wavelength laser source (Orbits-Lightwave) at the wavelength of 1554 nm, which was phase modulated by 2 sinusoidal tones with frequencies of 100 and 300 MHz in order to suppress the stimulated Brillouin scattering (SBS). The pump source was then boosted by an EDFA.

The signal was generated by a tunable laser source and combined with the pump using a wavelength division multiplexing (WDM) coupler. Both the pump and the signal then entered the copier and a phase conjugated copy of the signal, the idler was generated through FWM. Signal and pump power into the copier was −10 dBm and 30 dBm respectively. The copier consisted of two strained Aluminium-doped highly nonlinear fibers (HNLFs) with an isolator between them [18

18. C. Lundström, R. Malik, L. Gruner-Nielsen, B. Corcoran, S. L. I. Olsson, M. Karlsson, and P. A. Andrekson, “Fiber optic parametric amplifier with 10-dB net gain without pump dithering,” Photon. Tech. Lett. 25(3), 234–237 (2013). [CrossRef]

], and provided about 10 dB of on-off gain. The total length of the HNLF was 230 m with a nonlinear coefficient of 10W−1km−1. The average zero-dispersion wavelength (ZDWL) of the fiber was 1542 nm. After the copier, the signal-idler pair was split from the pump into two separate arms. In the signal-idler arm an optical processor (OP1, Finisar Waveshaper) was used to control temporal and phase characteristics of the signal and the idler necessary for the tuning of phase-matching condition in PSA. OP1 was also used for adjusting the desired signal-idler input power ratios at the input of the PSA. In the pump arm we used a pump recovery unit consisting of three cascaded EDFAs to boost the pump power. The signal-idler pair and the pump were recombined through a WDM and launched into the PSA. The PSA also consisted of two strained Al-doped HNLFs with an isolator in between and provided an on-off gain of 17 dB (11 dB) in PS (PI) mode. The total length of the HNLF was 300 m with a nonlinear coefficient of 10 W−1km−1. The average ZDWL of this fiber was 1539 nm. A phase locked loop (PLL) was used to keep the phase between signal, idler and pump stable against the mechanical and thermal drifts. The noise loading part consisted of a cascade of two EDFAs followed by a multi-wavelength optical filter. It was used to filter the noise in signal and idler bands only as well as to apply losses to vary signal-idler OSNR ratio at the input of the PSA. For OSNR measurements a polarizer followed by an optical spectrum analyzer (OSA) was used. The polarizer was used so that the noise only in the signal/idler polarization was measured. Fig. 2 shows the ΔOSNR (OSNR at the output relative to that at the input of the PSA) for both the signal (blue circles) and the idler waves (red stars) versus the input idler – input signal OSNR difference. At point B in the Fig. 2, where the input idler – input signal OSNR difference is zero and the coupled noise level (−45 dBm) is significantly higher than the quantum level (−61 dBm @ 0.1 nm bandwidth [3

3. E. Desurvire, Erbium-Doped Fiber Amplifiers: Principles and Applications (John Wiley & Sons, (1994).

]), the ΔOSNR is 2.7 dB (close to theoretical 3 dB) as also shown in [13

13. B. Corcoran, R. Malik, S. L. I. Olsson, C. Lundström, M. Karlsson, and P. A. Andrekson, “Noise beating in hybrid phase-sensitive amplifier systems,” Opt. Express 22(5), 5762–5771 (2014). [CrossRef] [PubMed]

]. The signal ΔOSNR varies from a 3 dB to a 5.5 dB as idler input OSNR is increased while keeping the signal input OSNR constant. Also, as the idler input OSNR is degraded in comparison to signal input OSNR by injecting more noise into the idler band, the signal output ΔOSNR varies from a 3 dB to a −10 dB behaving almost linearly. For the idler output ΔOSNR case as idler input OSNR is degraded the output OSNR improves from a 3 to a 6 dB. On the contrary, when idler input OSNR is improved then its output OSNR degrades from a 3 to −10 dB. Solid lines in Fig. 2 were calculated based on Eq. (9) and they depict the corresponding theoretical curves which match quite well with the experimental results.
Fig. 2 PSA output - input OSNR difference versus the input idler – input signal OSNR difference. Experimental points are depicted by circles (signal) and stars (idler) while solid lines are for theory using Eq. (9).

The advantage of the PSA as a noiseless amplifier starts to diminish for lower gain (<10 dB) [19

19. M. Vasilyev, “Distributed phase-sensitive amplification,” Opt. Express 13(19), 7563–7571 (2005). [CrossRef] [PubMed]

]. Here we have measured the OSNR improvements versus PSA gain under high and unbalanced noise loading regime. Figure 5 shows the output ΔOSNR versus the gain of the PSA. To begin with signal and idler OSNRs were unbalanced by 10 dB and PSA was set to) of input-output OSNR difference. As we reduce the gain by injecting less pump power into the PSA the improvement in OSNR starts to reduce. The theoretical curve based on Eq. (3), matches very well with the experimental data. By simplifying the equation and considering that we ignore the noise on the idler wave (as the noise on the signal is much higher) it can be easily seen thatΔOSNR sig=21/G+2(11/G)1/2. Therefore to have a full advantage of the PSA it is necessary to have a minimum PSA gain of at least 20 dB.
Fig. 5 OSNR improvement versus PSA gain under unbalanced noise loading scenario. Red circles are for experimental data points and solid line is for theory from Eqs. (3-6).

Fig. 6 BER curves for different noise loading scenarios.
Next we performed bit error rate (BER) tests for imbalanced noise loading. Figure 6 shows BER measurements of the signal output for four different situations: phase–insensitive (PI, black squares) and phase-sensitive with balanced noise (PS-B, blue pentagons), with signal OSNR lower than idler OSNR by 10 dB, corresponding to pint C in Fig. 2, (PS-SigLow-IdlHigh, red stars) and with signal OSNR higher than idler OSNR by 10 dB, corresponding to pint A in Fig. 2, (PS-SigHigh-IdlLow, magenta circles). When signal and idler have balanced input OSNRs a sensitivity improvement of 2.7 dB was measured, close to value from OSNR measurements. For signal input OSNR significantly lower than idler input OSNR a sensitivity improvement of 5.8 dB was measured, again close to the measured OSNR improvement. On the other hand for signal input OSNR significantly higher than idler input OSNR a sensitivity degradation of 6 dB was measured, again close to the value from OSNR measurements.

4. Discussion

This study both theoretically and experimentally confirms that the improvement that PSA provides depends upon the input OSNR ratio of both waves (modes). Therefore it becomes important when we have PI amplifiers before PSA to choose carefully the location of the signal and the idler waves within their gain spectra. Up to now PSAs have shown inherent properties of not deteriorating signal OSNR, but here we have shown that the PSA can be efficiently used to restore a deteriorated OSNR wave.

5. Conclusion

We have investigated unbalanced noise as well as unbalanced signal-idler beating in a PSA and have shown the OSNR improvements for the lower input OSNR wave in excess of 20 dB. A simple theory was formulated which matches the experimental results very well. BER tests were performed to verify the OSNR measurements. This can be very useful in restoring low OSNR signals at the expense of other phase-locked sidebands.

Acknowledgments

This work is supported by the Swedish Research Council, by the European Research Council under grant agreement ERC-2011-AdG - 291618 PSOPA and by the K.A. Wallenberg Foundation.

References and links

1.

C. M. Caves, “Quantum limits on noise in linear amplifiers,” Phys. Rev. D Part. Fields 26(8), 1817–1839 (1982). [CrossRef]

2.

C. E. Shannon, “Communication in the presence of noise,” Proc. Inst. Radio Eng. 37(1), 10–21 (1949).

3.

E. Desurvire, Erbium-Doped Fiber Amplifiers: Principles and Applications (John Wiley & Sons, (1994).

4.

D. J. Lovering, J. A. Levenson, P. Vidakovic, J. Webjörn, and P. S. Russell, “Noiseless optical amplification in quasi-phase-matched bulk lithium niobate,” Opt. Lett. 21(18), 1439–1441 (1996). [CrossRef] [PubMed]

5.

B. J. Puttnam, D. Mazroa, S. Shinada, and N. Wada, “Phase-squeezing properties of non-degenerate PSAs using PPLN waveguides,” Opt. Express 19(26), B131–B139 (2011). [CrossRef] [PubMed]

6.

Z. Tong, C. Lundström, C. J. McKinstrie, P. A. Andrekson, M. Karlsson, and A. Bogris, “Ultralow noise, broadband phase-sensitive optical Amplifiers, and their applications,” IEEE J. Sel. Top. Quantum Electron. 18(2), 1016–1032 (2012). [CrossRef]

7.

B. Corcoran, S. L. I. Olsson, C. Lundström, M. Karlsson, and P. Andrekson, “Phase-sensitive optical pre-amplifier implemented in an 80km DQPSK link,” Proc. OFC 2012, PDP5A (2012). [CrossRef]

8.

K. Croussore and G. Li, “Phase regeneration of NRZ-DPSK signals based on symmetric-pump phase-sensitive amplification,” IEEE Photon. Technol. Lett. 19(11), 864–866 (2007). [CrossRef]

9.

Z. Tong, C. Lundström, P. A. Andrekson, C. J. McKinstrie, M. Karlsson, D. J. Blessing, E. Tipsuwannakul, B. J. Puttnam, H. Toda, and L. Grüner-Nielsen, “Towards ultrasensitive optical links enabled by low-noise phase sensitive amplifiers,” Nat. Photonics 5(7), 430–436 (2011). [CrossRef]

10.

S.-K. Choi, M. Vasilyev, and P. Kumar, “Noiseless optical amplification of images,” Phys. Rev. Lett. 83(10), 1938–1941 (1999). [CrossRef]

11.

Z. Tong, A. O. J. Wiberg, E. Myslivets, B. P. P. Kuo, N. Alic, and S. Radic, “Broadband parametric multicasting via four-mode phase-sensitive interaction,” Opt. Express 20(17), 19363–19373 (2012). [CrossRef] [PubMed]

12.

T. Umeki, M. Asobe, H. Takara, Y. Miyamoto, and H. Takenouchi, “Multi-span transmission using phase and amplitude regeneration in PPLN-based PSA,” Opt. Express 21(15), 18170–18177 (2013). [CrossRef] [PubMed]

13.

B. Corcoran, R. Malik, S. L. I. Olsson, C. Lundström, M. Karlsson, and P. A. Andrekson, “Noise beating in hybrid phase-sensitive amplifier systems,” Opt. Express 22(5), 5762–5771 (2014). [CrossRef] [PubMed]

14.

Z. Tong, C. Lundström, M. Karlsson, M. Vasilyev, and P. A. Andrekson, “Noise performance of a frequency nondegenerate phase-sensitive amplifier with unequalized inputs,” Opt. Lett. 36(5), 722–724 (2011). [CrossRef] [PubMed]

15.

Z. Tong, A. Bogris, C. Lundström, C. J. McKinstrie, M. Vasilyev, M. Karlsson, and P. A. Andrekson, “Modeling and measurement of the noise figure of a cascaded non-degenerate phase-sensitive parametric amplifier,” Opt. Express 18(14), 14820–14835 (2010). [CrossRef] [PubMed]

16.

C. J. McKinstrie, S. Radic, and M. G. Raymer, “Quantum noise properties of parametric amplifiers driven by two pump waves,” Opt. Express 12(21), 5037–5066 (2004). [CrossRef] [PubMed]

17.

Z. Tong and S. Radic, “Low-noise optical amplification and signal processing in parametric devices,” Adv. Opt. Photon. 5(3), 318–384 (2013). [CrossRef]

18.

C. Lundström, R. Malik, L. Gruner-Nielsen, B. Corcoran, S. L. I. Olsson, M. Karlsson, and P. A. Andrekson, “Fiber optic parametric amplifier with 10-dB net gain without pump dithering,” Photon. Tech. Lett. 25(3), 234–237 (2013). [CrossRef]

19.

M. Vasilyev, “Distributed phase-sensitive amplification,” Opt. Express 13(19), 7563–7571 (2005). [CrossRef] [PubMed]

20.

R. Jha, S. Chand, and B. D. Gupta, “Fabrication and characterization of a surface plasmon resonance based fiber-optic sensor for bittering component—Naringin,” Sensor. Actuat. Biol. Chem. 115(1), 344–348 (2006).

21.

E. Pickwell and V. P. Wallace, “Biomedical applications of terahertz technology,” J. Phys. D Appl. Phys. 39(17), 301–310 (2006). [CrossRef]

22.

A. Mahjoubfar, K. Goda, G. Betts, and B. Jalali, “Optically amplified detection for biomedical sensing and imaging,” J. Opt. Soc. Am. A 30(10), 2124–2132 (2013). [CrossRef] [PubMed]

OCIS Codes
(060.2320) Fiber optics and optical communications : Fiber optics amplifiers and oscillators
(190.4380) Nonlinear optics : Nonlinear optics, four-wave mixing
(190.4970) Nonlinear optics : Parametric oscillators and amplifiers

ToC Category:
Optical Communications

History
Original Manuscript: March 7, 2014
Revised Manuscript: April 12, 2014
Manuscript Accepted: April 16, 2014
Published: April 23, 2014

Citation
R. Malik, A. Kumpera, S.L.I. Olsson, P.A. Andrekson, and M. Karlsson, "Optical signal to noise ratio improvement through unbalanced noise beating in phase-sensitive parametric amplifiers," Opt. Express 22, 10477-10486 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-9-10477


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References

  1. C. M. Caves, “Quantum limits on noise in linear amplifiers,” Phys. Rev. D Part. Fields 26(8), 1817–1839 (1982). [CrossRef]
  2. C. E. Shannon, “Communication in the presence of noise,” Proc. Inst. Radio Eng. 37(1), 10–21 (1949).
  3. E. Desurvire, Erbium-Doped Fiber Amplifiers: Principles and Applications (John Wiley & Sons, (1994).
  4. D. J. Lovering, J. A. Levenson, P. Vidakovic, J. Webjörn, P. S. Russell, “Noiseless optical amplification in quasi-phase-matched bulk lithium niobate,” Opt. Lett. 21(18), 1439–1441 (1996). [CrossRef] [PubMed]
  5. B. J. Puttnam, D. Mazroa, S. Shinada, N. Wada, “Phase-squeezing properties of non-degenerate PSAs using PPLN waveguides,” Opt. Express 19(26), B131–B139 (2011). [CrossRef] [PubMed]
  6. Z. Tong, C. Lundström, C. J. McKinstrie, P. A. Andrekson, M. Karlsson, A. Bogris, “Ultralow noise, broadband phase-sensitive optical Amplifiers, and their applications,” IEEE J. Sel. Top. Quantum Electron. 18(2), 1016–1032 (2012). [CrossRef]
  7. B. Corcoran, S. L. I. Olsson, C. Lundström, M. Karlsson, and P. Andrekson, “Phase-sensitive optical pre-amplifier implemented in an 80km DQPSK link,” Proc. OFC 2012, PDP5A (2012). [CrossRef]
  8. K. Croussore, G. Li, “Phase regeneration of NRZ-DPSK signals based on symmetric-pump phase-sensitive amplification,” IEEE Photon. Technol. Lett. 19(11), 864–866 (2007). [CrossRef]
  9. Z. Tong, C. Lundström, P. A. Andrekson, C. J. McKinstrie, M. Karlsson, D. J. Blessing, E. Tipsuwannakul, B. J. Puttnam, H. Toda, L. Grüner-Nielsen, “Towards ultrasensitive optical links enabled by low-noise phase sensitive amplifiers,” Nat. Photonics 5(7), 430–436 (2011). [CrossRef]
  10. S.-K. Choi, M. Vasilyev, P. Kumar, “Noiseless optical amplification of images,” Phys. Rev. Lett. 83(10), 1938–1941 (1999). [CrossRef]
  11. Z. Tong, A. O. J. Wiberg, E. Myslivets, B. P. P. Kuo, N. Alic, S. Radic, “Broadband parametric multicasting via four-mode phase-sensitive interaction,” Opt. Express 20(17), 19363–19373 (2012). [CrossRef] [PubMed]
  12. T. Umeki, M. Asobe, H. Takara, Y. Miyamoto, H. Takenouchi, “Multi-span transmission using phase and amplitude regeneration in PPLN-based PSA,” Opt. Express 21(15), 18170–18177 (2013). [CrossRef] [PubMed]
  13. B. Corcoran, R. Malik, S. L. I. Olsson, C. Lundström, M. Karlsson, P. A. Andrekson, “Noise beating in hybrid phase-sensitive amplifier systems,” Opt. Express 22(5), 5762–5771 (2014). [CrossRef] [PubMed]
  14. Z. Tong, C. Lundström, M. Karlsson, M. Vasilyev, P. A. Andrekson, “Noise performance of a frequency nondegenerate phase-sensitive amplifier with unequalized inputs,” Opt. Lett. 36(5), 722–724 (2011). [CrossRef] [PubMed]
  15. Z. Tong, A. Bogris, C. Lundström, C. J. McKinstrie, M. Vasilyev, M. Karlsson, P. A. Andrekson, “Modeling and measurement of the noise figure of a cascaded non-degenerate phase-sensitive parametric amplifier,” Opt. Express 18(14), 14820–14835 (2010). [CrossRef] [PubMed]
  16. C. J. McKinstrie, S. Radic, M. G. Raymer, “Quantum noise properties of parametric amplifiers driven by two pump waves,” Opt. Express 12(21), 5037–5066 (2004). [CrossRef] [PubMed]
  17. Z. Tong, S. Radic, “Low-noise optical amplification and signal processing in parametric devices,” Adv. Opt. Photon. 5(3), 318–384 (2013). [CrossRef]
  18. C. Lundström, R. Malik, L. Gruner-Nielsen, B. Corcoran, S. L. I. Olsson, M. Karlsson, P. A. Andrekson, “Fiber optic parametric amplifier with 10-dB net gain without pump dithering,” Photon. Tech. Lett. 25(3), 234–237 (2013). [CrossRef]
  19. M. Vasilyev, “Distributed phase-sensitive amplification,” Opt. Express 13(19), 7563–7571 (2005). [CrossRef] [PubMed]
  20. R. Jha, S. Chand, B. D. Gupta, “Fabrication and characterization of a surface plasmon resonance based fiber-optic sensor for bittering component—Naringin,” Sensor. Actuat. Biol. Chem. 115(1), 344–348 (2006).
  21. E. Pickwell, V. P. Wallace, “Biomedical applications of terahertz technology,” J. Phys. D Appl. Phys. 39(17), 301–310 (2006). [CrossRef]
  22. A. Mahjoubfar, K. Goda, G. Betts, B. Jalali, “Optically amplified detection for biomedical sensing and imaging,” J. Opt. Soc. Am. A 30(10), 2124–2132 (2013). [CrossRef] [PubMed]

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