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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 16, Iss. 14 — Jul. 7, 2008
  • pp: 10091–10097
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Evidence of ultra low microwave additive phase noise for an optical RF link based on a class-A semiconductor laser.

Ghaya Baili, Mehdi Alouini, Thierry Malherbe, Daniel Dolfi, Jean-Pierre Huignard, Thomas Merlet, Jean Chazelas, Isabelle Sagnes, and Fabien Bretenaker  »View Author Affiliations


Optics Express, Vol. 16, Issue 14, pp. 10091-10097 (2008)
http://dx.doi.org/10.1364/OE.16.010091


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Abstract

The additive RF phase noise of a microwave photonics link is measured using, as the optical source, a semiconductor laser operating in the class-A regime. The relative intensity noise of this laser being below the shot noise relative level, the phase noise floor of the link is shown to be shot noise limited, −152 dBc/Hz in our experimental conditions. As a result, the phase noise floor evolves as the inverse of the detected photocurrent, pushing the limits of performance to the availability of high power photo-detectors. Below 6 kHz from the carrier frequency at 3GHz, some noise, in excess with respect to the shot noise limit, is observed but remains lower than −110 dBc/Hz at 100 Hz offset frequency. This residual noise originates mainly from environmental noise and can be reduced by isolating the laser from acoustic/electromagnetic perturbations.

© 2008 Optical Society of America

1. Introduction

2. Experimental arrangement

Fig. 1. The experimental set-up used to assess the impact of the laser on the RF phase noise of a microwave photonics link. (1) Reference arm including coarse (Δτ) and fine (φ) time delay adjustment and a RF attenuator (Att.). (2) Arm containing the optical link under test followed by a low noise RF amplifier (G) and a RF attenuator (Att.) The optical link is composed of the low noise class-A laser, a Mach-Zehnder modulator (MZM), an optical fiber and a high frequency low noise photodiode (D).

Let us remind that in the peculiar case of radar applications which we address here, the spectral range of interest is 100Hz-1MHz. This spectral region covers the Doppler shift of classical moving objects (aircrafts or ground vehicles). For instance, if one considers an aircraft flying at 1000 ms-1 along the radar line-of-sight, then the observed Doppler shift is 20 kHz only, at 3 GHz. Thus, unlike in telecom applications where the spectral range of interest can extend up to several GHz, the spectral region above 1 MHz does not contain any useful information.

3. Results and discussion

Pfloor(fc)=12R(kBTR+2eIph+RIN(fc)Iph2)
(1)

where R is the photodiode load impedance (50 Ω), kB Boltzman’s constant, e the elementary charge, Iph the average detected photocurrent, and RIN(fc) the relative intensity noise of the laser at the modulation frequency fc. In this expression, the laser relative intensity noise RIN(fc) accounts for the optical excess noise independent from the shot noise. Consequently, if the laser intensity is shot noise limited, i.e., RIN(fc)≪2eIph, its contribution can be neglected. Since, in our case, the thermal noise is also negligible as compared to the shot noise level, Eq. (1) then simplifies to:

Pfloor(fc)=eIphR
(2)

Finally, the additive phase noise Lfloor(fc), being given by the ratio between the phase noise and the signal power, we end up with the following simple expression :

Lfloor(fc)=2em2Iph
(3)

Fig. 2. Additive phase noise spectra. (a) Plot 1 : optical modulation index and detected photocurrent are respectively 26% and 1.2 mA. Plot 2 : optical modulation index and detected photocurrent are respectively 59% and 1.59 mA. Plot 3 : Measured noise floor when the optical link is replaced by an RF cable. (b) The Product m 2 Lfloor (m : optical modulation index, Lfloor : additive phase noise floor) evolves as the inverse of the detected photocurrent (Iph), proving that the phase noise is actually shot noise limited.

Let us now consider the low frequency part of phase noise spectra, namely below 6 kHz [region (I) of Fig. 2(b)]. In this spectral region, the RF phase noise is no longer shot noise limited. It behaves like a plateau whose level is independent of the modulation index m (see Fig. 2). This is the signature of multiplicative noise which usually has a technical origin. In order to test this hypothesis we have covered the laser and its pump source with a set of thick metallic panels. This very basic acoustic/electromagnetic isolation scheme leads to a significant reduction of the phase noise close to the carrier (for instance 15 dB at 1 kHz), as shown in Fig. 3. We believe that this residual low frequency phase noise could be further reduced by designing an efficient acoustic and electromagnetic insulation housing, and could even be cancelled with a monolithic cavity design.

Fig. 3. Additive phase noise spectra. Plot 1 : same as plot 2 of Fig.2, The optical modulation index and the detected photocurrent are respectively 59% and 1.59 mA. Plot 2 : the laser is covered with basic acoustic/electromagnetic insulation panels. The optical modulation index and the detected photocurrent are respectively 30% and 1.8 mA. Plot 3 : Measured noise floor when the optical link is replaced by an RF cable.

Fig. 4. Comparison between additive phase noise spectra when the semiconductor class-A laser (plot 1) and the solid-state Mephisto laser (plot 2) are implemented in the microwave photonics link. The optical modulation index and the detected photocurrent are respectively 30% and 1.8 mA for the class-A laser, and respectively 53% and 1.73 mA for the solid-state Mephisto laser. Plot 3 is the measurement noise floor. The dashed line displays the shot noise level.

4. Conclusion

Acknowledgments

Authors would like to acknowledge Emmanuel Poitiers, Christophe Feuillet, and Morgan Quéguiner for their kind help.

References and links

1.

S. Blanc, S. Formont, D. Dolfi, S. Tonda-Goldstein, N. Vodjdani, G. Auvray, S. Blanc, C. Fourdin, Y. Canal, and J. Chazelas, “Photonics for RF signal processing in radar systems,” in 2004 International Topical Meeting on Microwave Photonics (IEEE/LEOS, Piscataway, NJ, 2004), 305–308 (2004).

2.

C. H. Cox III, E. I. Ackerman, G. E. Betts, and J. L. Prince, “Limits on the performance of RF-over-fiber links and their impact on device design,” IEEE Trans. Microwave Theory Tech. 54, 906–920 (2006). [CrossRef]

3.

S. Blanc, M. Alouini, K. Garenaux, M. Queguiner, and T. Merlet, “Optical Multibeamforming Network based on WDM and Dispersion Fiber in Receive Mode,” IEEE. Trans. Microwave Theory Tech. 54, 402–411 (2006). [CrossRef]

4.

A. J. Seeds and K. J. Williams, “Microwave photonics,” J. of Lightwave Technol. 24, 4628–4641 (2006). [CrossRef]

5.

G. Qi, J. Yao, J. Seregelyi, S. Paquet, C. Bésisle, X. Zhang, K. Wu, and R. Kashyap, “Phase-noise analysis of optically generated millimeter-wave signals with external optical modulation techniques,” J. Lightwave Technol. 24, 4861–4875 (2006). [CrossRef]

6.

A. S. Daryoush, “Phase coherency of generated millimeter wave signals using fiber optic distribution of a reference,” in 1996 International Topical Meeting on Microwave Photonics (IEEE/LEOS, Kyoto Japan, 1996), Technical DigestWE4-3, 225–228 (1996).

7.

M. Bibey, F. Debrogies, M. Krakowski, and D. Mongardien, “Very low phase-noise optical links-experiments and theory,” IEEE Trans. Microwave Theory Tech 47, 2257–2261 (1999). [CrossRef]

8.

P. J. Matthews, P. D. Biernacki, and R. D. Esman, “RF Phase-noise performance of a two-channel optical downconverting link for microwave phase detection,” IEEE Photon. Technol. Lett. 10, 594–596 (1998). [CrossRef]

9.

G. Baili, M. Alouini, C. Moronvalle, D. Dolfi, and F. Bretenaker, “Broad-bandwidth shot-noise-limited class-A operation of a monomode semiconductor fiber-based ring laser,” Opt. Lett. 31, 62–64 (2006). [CrossRef] [PubMed]

10.

G. Baili, M. Alouini, D. Dolfi, F. Bretenaker, I. Sagnes, and A. Garnache, “Shot-noise-limited operation of a monomode high-cavity-finesse semiconductor laser for microwave photonics applications,” Opt. Lett. 32, 650–652 (2007). [CrossRef] [PubMed]

11.

G. Baili, F. Bretenaker, M. Alouini, L. Morvan, D. Dolfi, and I. Sagnes, “Experimental investigation and analytical modeling of excess intensity noise in semiconductor class-A lasers,” J. Lightwave Technol. 26, 952–961 (2008). [CrossRef]

12.

M. Jacquemet, M. Domenech, G. Lucas-Leclin, J. Dion, M. Strassner, I. Sagnes, and A. Garnache, “Singlefrequency cw certical external cavity surface emitting semiconductor laser at 1003 nm and 501 nm by intracavity frequency doubling,” Appl. Phys. B 86, 503–510 (2007). [CrossRef]

13.

http://www.innolight.de/.

OCIS Codes
(060.2360) Fiber optics and optical communications : Fiber optics links and subsystems
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(140.5960) Lasers and laser optics : Semiconductor lasers
(270.2500) Quantum optics : Fluctuations, relaxations, and noise
(350.4010) Other areas of optics : Microwaves
(060.5625) Fiber optics and optical communications : Radio frequency photonics

ToC Category:
Lasers and Laser Optics

History
Original Manuscript: April 1, 2008
Revised Manuscript: May 18, 2008
Manuscript Accepted: June 16, 2008
Published: June 23, 2008

Citation
Ghaya Baili, Mehdi Alouini, Thierry Malherbe, Daniel Dolfi, Jean-Pierre Huignard, Thomas Merlet, Jean Chazelas, Isabelle Sagnes, and Fabien Bretenaker, "Evidence of ultra low microwave additive phase noise for an optical RF link based on a class-A semiconductor laser," Opt. Express 16, 10091-10097 (2008)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-14-10091


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References

  1. S. Blanc, S. Formont, D. Dolfi, S. Tonda-Goldstein, N. Vodjdani, G. Auvray, S. Blanc, C. Fourdin, Y. Canal, and J. Chazelas, "Photonics for RF signal processing in radar systems," in 2004 International Topical Meeting on Microwave Photonics (IEEE/LEOS, Piscataway, NJ, 2004), 305-308 (2004).
  2. C. H. CoxIII, E. I. Ackerman, G. E. Betts, J. L. Prince, "Limits on the performance of RF-over-fiber links and their impact on device design," IEEE Trans. Microwave Theory Tech. 54, 906-920 (2006). [CrossRef]
  3. S. Blanc, M. Alouini, K. Garenaux, M. Queguiner, and T. Merlet, "Optical Multibeamforming Network based on WDM and Dispersion Fiber in Receive Mode," IEEE. Trans. Microwave Theory Tech. 54, 402-411 (2006). [CrossRef]
  4. A. J. Seeds and K. J. Williams, "Microwave photonics," J. of Lightwave Technol. 24, 4628-4641 (2006). [CrossRef]
  5. G. Qi, J. Yao, J. Seregelyi, S. Paquet, C. Bésisle, X. Zhang, K. Wu, and R. Kashyap, "Phase-noise analysis of optically generated millimeter-wave signals with external optical modulation techniques," J. Lightwave Technol. 24, 4861-4875 (2006). [CrossRef]
  6. A. S. Daryoush, "Phase coherency of generated millimeter wave signals using fiber optic distribution of a reference," in 1996 International Topical Meeting on Microwave Photonics (IEEE/LEOS, Kyoto Japan, 1996), Technical Digest WE4-3, 225-228 (1996).
  7. M. Bibey, F. Debrogies, M. Krakowski, and D. Mongardien, "Very low phase-noise optical links-experiments and theory," IEEE Trans. Microwave Theory Tech 47, 2257-2261 (1999). [CrossRef]
  8. P. J. Matthews, P. D. Biernacki, and R. D. Esman, "RF Phase-noise performance of a two-channel optical downconverting link for microwave phase detection," IEEE Photon. Technol. Lett. 10, 594-596 (1998). [CrossRef]
  9. G. Baili, M. Alouini, C. Moronvalle, D. Dolfi, and F. Bretenaker, "Broad-bandwidth shot-noise-limited class-A operation of a monomode semiconductor fiber-based ring laser," Opt. Lett. 31, 62-64 (2006). [CrossRef] [PubMed]
  10. G. Baili, M. Alouini, D. Dolfi, F. Bretenaker, I. Sagnes, and A. Garnache, "Shot-noise-limited operation of a monomode high-cavity-finesse semiconductor laser for microwave photonics applications," Opt. Lett. 32, 650-652 (2007). [CrossRef] [PubMed]
  11. G. Baili, F. Bretenaker, M. Alouini, L. Morvan, D. Dolfi, and I. Sagnes, "Experimental investigation and analytical modeling of excess intensity noise in semiconductor class-A lasers," J. Lightwave Technol. 26, 952-961 (2008). [CrossRef]
  12. M. Jacquemet, M. Domenech, G. Lucas-Leclin, J. Dion, M. Strassner, I. Sagnes and A. Garnache, "Single-frequency cw certical external cavity surface emitting semiconductor laser at 1003 nm and 501 nm by intracavity frequency doubling," Appl. Phys. B 86, 503-510 (2007). [CrossRef]
  13. http://www.innolight.de/.

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