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Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 21 — Oct. 11, 2010
  • pp: 21573–21584
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Suppression of phase-induced intensity noise in fibre optic delay line signal processors using an optical phase modulation technique

Erwin H. W. Chan  »View Author Affiliations


Optics Express, Vol. 18, Issue 21, pp. 21573-21584 (2010)
http://dx.doi.org/10.1364/OE.18.021573


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Abstract

A technique that can suppress the dominant phase-induced intensity noise in fibre optic delay line signal processors is presented. It is based on phase modulation of the optical carrier to distribute the phase noise at the information band into a high frequency band which can be filtered out. This technique is suitable for suppressing the phase noise in various delay line structures and for integrating in the conventional fibre optic links. It can also suppress the coherent interference effect at the same time. A model for predicting the amount of phase noise reduction in various delay line structures using the optical phase modulation technique is presented for the first time and is experimentally verified. Experimental results demonstrate the technique can achieve a large phase noise reduction in various fibre optic delay line signal processors.

© 2010 OSA

1. Introduction

Microwave photonic systems for the distribution of signals have been the subject of significant interest. Photonic signal processing is attractive because it has the potential to overcome existing electronic bottlenecks for processing wide bandwidth signals. Moreover, it is immune to electromagnetic interference and compatible with the existing optical networks.

A range of fibre optic delay line filter structures have been reported [1

1. B. Moslehi and J. W. Goodman, “Novel amplified fiber-optic recirculating delay line processor,” J. Lightwave Technol. 10(8), 1142–1147 (1992). [CrossRef]

10

10. M. Y. Frankel and R. D. Esman, “Fiber-optic tunable microwave transversal filter,” IEEE Photon. Technol. Lett. 7(2), 191–193 (1995). [CrossRef]

]. In order to obtain a robust transfer characteristic irrespective of environmental perturbations, the filters based on a single laser and a single photodetector in a delay line structure [1

1. B. Moslehi and J. W. Goodman, “Novel amplified fiber-optic recirculating delay line processor,” J. Lightwave Technol. 10(8), 1142–1147 (1992). [CrossRef]

8

8. E. H. W. Chan and R. A. Minasian, “Reflective amplified recirculating delay line bandpass filter,” J. Lightwave Technol. 25(6), 1441–1446 (2007). [CrossRef]

] require the use of an incoherent approach, in which the coherence time of the light source is made smaller than the minimum delay time of the processor. However, the problem with this incoherent approach is that it generates an excessive amount of phase-induced intensity noise (PIIN) due to the beating of the delayed optical signals at the photodetector [11

11. M. Tur and A. Arie, “Phase induced intensity noise in concatenated fiber-optic delay lines,” J. Lightwave Technol. 6(1), 120–130 (1988). [CrossRef]

13

13. J. T. Kringlebotn and K. Blotekjaer, “Noise analysis of an amplified fiber-optic recirculating delay line,” J. Lightwave Technol. 12(3), 573–582 (1994). [CrossRef]

]. The phase noise can severely degrade the signal-to-noise ratio (SNR), which limits the use of fibre optic delay line signal processors in practice.

2. Delay line signal processor phase noise reduction unit

The PIIN spectrum generated by an incoherent fibre optic delay line signal processor can be expressed as the product of two independent terms [11

11. M. Tur and A. Arie, “Phase induced intensity noise in concatenated fiber-optic delay lines,” J. Lightwave Technol. 6(1), 120–130 (1988). [CrossRef]

,12

12. B. Moslehi, “Analysis of optical phase noise in fiber-optic systems employing a laser source with arbitrary coherence time,” J. Lightwave Technol. 4(9), 1334–1351 (1986). [CrossRef]

]. One is referred to as the source dependent term, which is only dependent on the optical source characteristic. The other is referred to as the structure dependent term, which is only dependent on the delay line signal processor configuration. This implies that the signal processor PIIN can be reduced by altering either the optical source characteristic or the signal processor configuration. Since the signal processor configuration determines the frequency response performance, the optical source characteristic is modified for phase noise reduction as such modification has no effect on the signal processor frequency response as long as the system is operating in the incoherent regime. A simple way to modify the optical source characteristic is to apply phase modulation to the optical carrier.

3. Phase noise suppression by single tone phase modulation

Consider the structure shown in Fig. 1 where the intensity modulated optical signal is phase modulated by a single frequency tone and is then launched into an unbalanced Mach Zehnder interferometer (UMZI) notch filter formed by connecting two optical couplers with a length difference between the two arms [17

17. A. H. Quoc and S. Tedjini, “Experimental investigation on the optical unbalanced Mach-Zehnder interferometers as microwave filters,” IEEE Microwave Guided Wave Lett. 4(6), 183–185 (1994). [CrossRef]

]. Since both the interferometric noise generated by double reflection and the PIIN generated by the UMZI are caused by the beating of two delayed optical signals at the photodetector, the UMZI notch filter PIIN spectrum after single tone phase modulation has the same behaviour as the interferometric noise spectrum after single tone phase modulation, which has been analysed in [15

15. A. Yariv, H. Blauvelt, D. Huff, and H. Zarem, “An experimental and theoretical study of the suppression of interferometric noise and distortion in AM optical links by phase dither,” J. Lightwave Technol. 15(3), 437–443 (1997). [CrossRef]

,16

16. P. K. Pepeljugoski and K. Y. Lau, “Interferometric noise reduction in fiber-optic links by superposition of high frequency modulation,” J. Lightwave Technol. 10(7), 957–963 (1992). [CrossRef]

]. Based on the result given in [16

16. P. K. Pepeljugoski and K. Y. Lau, “Interferometric noise reduction in fiber-optic links by superposition of high frequency modulation,” J. Lightwave Technol. 10(7), 957–963 (1992). [CrossRef]

], the UMZI notch filter PIIN spectrum after single tone phase modulation can be written as
SN,PM(f)={J02(A)SN(f)+n=1Jn2(A)[SN(fnf0)+SN(f+nf0)]}Sδ(f)
(1)
where Jn(x) is the Bessel function of n th order of first kind, Sδ(f) is the structure dependent term of the delay line signal processor PIIN, and SN(f) is the source dependent term of the delay line signal processor PIIN without superimposed modulation. Assuming the laser has a Lorentzian lineshape, SN(f) is given by [12

12. B. Moslehi, “Analysis of optical phase noise in fiber-optic systems employing a laser source with arbitrary coherence time,” J. Lightwave Technol. 4(9), 1334–1351 (1986). [CrossRef]

]
SN(f)=1/(πΔν)1+(f/Δν)2
(2)
where Δν is the laser linewidth. A in Eq. (1) is defined as
A=2asin(Ω0τ/2)
(3)
where a = πV 0/Vπ is the phase modulation index, V 0 is the voltage of the single tone into the phase modulator, Vπ is the half wave voltage of the phase modulator, Ω0 = 2πf 0 is the angular frequency of the single tone into the phase modulator and τ is the signal time delay. The term J 0 2(A) in Eq. (1) determines the amount of PIIN reduction by single tone phase modulation. As J 0 2(A) approaches zero the PIIN is distributed into the input single tone and its harmonic frequencies. Hence the PIIN at the information band is largely reduced. Since J 0 2(A) = 0 when A = −2.405, the phase modulation index required to minimise the PIIN generated by the UMZI notch filter at the information band is given by

a=1.2025sin(Ω0τ/2)
(4)

Figure 2
Fig. 2 UMZI notch filter PIIN spectrums with (dash) and without (solid) a 5.05 GHz frequency single tone phase modulation. The phase modulation index is 1.2. The signal time delay is 10 ns.
depicts the UMZI notch filter PIIN spectrums with and without single tone phase modulation.

The free spectral range (FSR) of the UMZI notch filter response is 100 MHz. The optical source has a linewidth of 200 MHz, which is larger than the filter FSR in order to avoid the coherent interference problem. The phase modulator is driven by a single tone with the frequency of 5.05 GHz and the phase modulation index is designed to be 1.2 so that J 0 2(A) = 0. As can be seen from the figure, by proper design of the phase modulation index, the UMZI notch filter PIIN is distributed into the input single tone frequency. A 29 dB PIIN reduction at the UMZI notch filter passband frequency of 100 MHz is obtained. The amount of PIIN reduction can be further increased by increasing the input single tone frequency while satisfying the condition J 0 2(A) = 0.

The time delay between the two taps generated by the UMZI notch filter affects the amount of phase noise reduction. Different signal time delays require different single tone frequencies and phase modulation indexes to obtain a large phase noise reduction. The phase noise generated by the multi-tap delay line signal processor is due to the beating of different delayed optical signals, which are separated by different times. Hence Eq. (1) cannot be used to predict the amount of phase noise reduction in multi-tap delay line signal processors after single tone phase modulation. A model was developed for the first time to obtain the amount of phase noise reduction in multi-tap delay line signal processors after single tone phase modulation. Consider a passive recirculating delay line (RDL) notch filter formed by connecting one of the outputs of a 33% coupling ratio optical coupler back to one of its inputs, which can be viewed as a three-tap device [12

12. B. Moslehi, “Analysis of optical phase noise in fiber-optic systems employing a laser source with arbitrary coherence time,” J. Lightwave Technol. 4(9), 1334–1351 (1986). [CrossRef]

]. The PIIN of the passive RDL notch filter is generated by the three taps beating with each other at the photodetector. In order to predict the amount of phase noise reduction after single tone phase modulation, the impulse response of the passive RDL notch filter is viewed as three sets of two-tap impulse response as shown in Fig. 3
Fig. 3 Passive RDL notch filter impulse response.
.

One can see from the figure that the time delay between the two taps in Set I and II is τ, whereas the time delay in Set III is 2τ. The two taps in each set beat with each other generating PIIN. The maximum amount of phase noise reduction by single tone phase modulation in the three-tap delay line structure is obtained by minimising the average of the sum of J 0 2(Ax) in each set, i.e.
X3,0=[2J02(A1)+J02(A2)]/3
(5)
where A 1 = −2asin(Ω0 τ/2) and A 2 = −2asin(Ω0 τ). Extending the above result to an m-tap delay line structure, the maximum amount of phase noise reduction by single tone phase modulation in an m-tap delay line structure is obtained by minimising the term Xm ,0, which is given by
Xm,0=x=1m1(mx)J02(Ax)/x=1m1(mx)
(6)
where Ax is defined as
Ax=2asin(Ω0xτ/2)
(7)
The m-tap delay line structure PIIN spectrum after single tone phase modulation can be written as
SN,PM(f)={Xm,0SN(f)+n=1Xm,n[SN(fnf0)+SN(f+nf0)]}Sδ(f)
(8)
Note that the term Xm ,0 in Eq. (8) cannot be cancelled by designing the single tone frequency and the phase modulation index when m>2. However, the single tone frequency and the phase modulation index can be designed to minimise Xm ,0 in order to maximise the amount of PIIN reduction.

Simulation results show that a large PIIN reduction of 28.8 dB can be obtained at the passband of the 100 MHz FSR passive RDL notch filter when the phase modulator is driven by a 5.033 GHz frequency single tone with a phase modulation index of 1.39. However, as the number of tap increases, the amount of PIIN reduction by single tone phase modulation decreases. It was found from the simulation that the amount of phase noise reduction in a 20-tap delay line structure is limited to 11.6 dB when the phase modulator is driven by a 5.005 GHz frequency signal tone with a phase modulation index of 5. This shows that the amount of phase noise reduction by single tone phase modulation is dependent on the number of taps generated by the delay line structure. A high-resolution signal processor has a large number of taps, as such a more complex signal than a single tone is needed to obtain a large phase noise reduction.

4. Phase noise reduction by Gaussian noise phase modulation

Distribution of the delay line signal processor PIIN can be done by increasing the linewidth of the optical source. A wide linewidth optical source results in a wide delay line signal processor phase noise spectrum. A wide PIIN spectrum means that the phase noise is distributed evenly in a wide frequency band and consequently the noise at the information band is reduced. It has been proposed and experimentally demonstrated that applying Gaussian noise phase modulation to the optical carrier can broaden the laser linewidth to avoid the coherent interference effect in fibre optic delay line signal processors [18

18. E. H. W. Chan and R. A. Minasian, “Optical source coherence controller for fibre optic delay line RF/microwave signal processors,” Opt. Commun. 254(1-3), 104–111 (2005). [CrossRef]

]. This technique can also be used to suppress the phase noise. In this case the amount of PIIN reduction is independent of the delay line signal processor configuration. The use of Gaussian noise phase modulation to increase the laser linewidth for phase noise suppression allows a narrow linewidth telecommunications-type laser to be used as an optical source. The phase noise reduction unit has the functions of suppressing both the PIIN and the coherent interference effect.

The autocorrelation function for a laser after bandpass Gaussian noise phase modulation is given by [16

16. P. K. Pepeljugoski and K. Y. Lau, “Interferometric noise reduction in fiber-optic links by superposition of high frequency modulation,” J. Lightwave Technol. 10(7), 957–963 (1992). [CrossRef]

]
RN,PM(δτ)=2Po2R(δτ)exp{2a2[Rn(0)Rn(δτ)cos(Ψ0δτ)]}
(9)
where
R(δτ)=exp[12τc(2|τ||τδτ||τ+δτ|+2|δτ|)]
(10)
Po is the average output laser power, τc is the laser coherence time, Rn(δτ) is the autocorrelation function of the Gaussian noise at the input of the phase modulator and Ψ0 is the noise centre angular frequency. The delay line signal processor PIIN spectrum after Gaussian noise phase modulation is given by
SN,PM(f)=Sδ(f)FT[RN,PM(δτ)]
(11)
where FT[x] is the Fourier transform of x. It can be seen from Eqs. (9) and (11) that the delay line signal processor PIIN spectrum after Gaussian noise phase modulation is dependent on the phase modulation index, which can be designed to reduce the PIIN at the information band. As an example, a high-resolution multi-tap delay line signal processor, e.g. an amplified RDL bandpass filter [1

1. B. Moslehi and J. W. Goodman, “Novel amplified fiber-optic recirculating delay line processor,” J. Lightwave Technol. 10(8), 1142–1147 (1992). [CrossRef]

], has a passband at 100 MHz. The frequency response of the signal processor has a FSR of 100 MHz. The linewidth of the optical source is designed to be 200 MHz, which is larger than the signal processor FSR, so that there is no coherent interference problem. Figure 4
Fig. 4 The amount of phase noise reduction and the broadened laser linewidth as a function of the phase modulation index when a 200 MHz linewidth laser undergoes a 1 GHz bandwidth Lorentzian shape Gaussian noise phase modulation.
depicts the amount of the delay line signal processor phase noise reduction and the broadened laser linewidth when the phase modulator is driven by a 1 GHz bandwidth Lorentzian shape Gaussian noise with different phase modulation indexes. It can be seen that a 26 dB phase noise reduction in a multi-tap delay line signal processor can be obtained by broadening the laser linewidth from 200 MHz to 95 GHz. The wider the laser linewidth, the more noise is distributed into high frequencies. Hence, a larger amount of phase noise reduction is obtained. Note that the width of the delay line signal processor phase noise spectrum after Gaussion noise phase modulation is mainly dependent on the input noise bandwidth and the phase modulation index. This means that it is not important to design the spectrum shape of the Gaussian noise. A wideband and high power Gaussian noise is the only requirement for laser linewidth broadening to reduce the delay line signal processor PIIN.

5. Experimental results

An experiment was set up to verify the suppression of a delay line structure PIIN using the single tone phase modulation technique. A DFB laser having a 3 MHz linewidth was used as an optical source. The optical source was phase modulated by a single tone with a phase modulation index of 1.45. The output of the phase modulator was connected to a Mach Zehnder interferometer having a long path length difference of around 100 m between the two arms to obtain a stable output insensitive to environmental perturbations. The output of the Mach Zehnder interferometer was detected by a photodetector. The output phase noise spectrum was viewed on an electrical spectrum analyser. Figure 5
Fig. 5 Measured (solid) and predicted (dots) PIIN spectrum of a two-tap delay line structure with and without single tone phase modulation. The phase modulation index is 1.45. The laser linewidth is 3 MHz. The signal time delay is 0.5 μs.
shows the experimental result together with the theoretical prediction of the phase noise spectrum when the phase modulator was driven by a single tone with different frequencies. The results demonstrate that, by properly adjusting the single tone frequency, one can distribute the phase noise at the baseband into the input single tone frequency.

Experiments were set up as shown in Fig. 1 to demonstrate the suppression of PIIN in various fibre optic delay line filters. The optical source was a tuneable laser operating at a wavelength of 1550 nm and having a narrow linewidth of less than 500 kHz. The laser linewidth was broadened by an optical source coherence controller [18

18. E. H. W. Chan and R. A. Minasian, “Optical source coherence controller for fibre optic delay line RF/microwave signal processors,” Opt. Commun. 254(1-3), 104–111 (2005). [CrossRef]

] to around 120 MHz and was launched into a quadrature biased electro-optic modulator (EOM). The EOM output was connected to a phase noise reduction unit consisting of a phase modulator having a half wave voltage of 6.8 V at 3 GHz and a microwave signal generator. It was followed by an UMZI notch filter [17

17. A. H. Quoc and S. Tedjini, “Experimental investigation on the optical unbalanced Mach-Zehnder interferometers as microwave filters,” IEEE Microwave Guided Wave Lett. 4(6), 183–185 (1994). [CrossRef]

] with a 6.6 m path length difference between the two arms. The output was detected by a photodetector. A notch filter response having a FSR of 30.4 MHz was measured on a network analyser. The PIIN spectrum was viewed on a spectrum analyser. A 26 dBm high power single tone was applied to a phase modulator with a 6.8 V half wave voltage in order to obtain a large phase modulation index of 2.92. Figure 6(a)
Fig. 6 (a) Measured and predicted amount of UMZI notch filter PIIN reduction after different frequency single tone phase modulation. The phase modulation index is 2.92. (b) Measured and predicted amount of UMZI notch filter PIIN reduction for different phase modulation indexes. The input single tone frequency is 3 GHz.
shows the measured and predicted amount of PIIN reduction at the UMZI notch filter passband after different frequency single tone phase modulation. A large phase noise reduction of over 30 dB was obtained when the single tone frequency was 3 GHz. The PIIN at the UMZI notch filter passband was measured for different input single tone power while the single tone frequency was fixed at 3 GHz. Figure 6(b) shows the comparison between the experimental result and the theoretical prediction of the amount of PIIN reduction at the UMZI notch filter passband for different phase modulation indexes. This shows a large PIIN reduction in an UMZI notch filter can be obtained by designing the single tone frequency and the phase modulation index.

The UMZI was replaced by a passive RDL [12

12. B. Moslehi, “Analysis of optical phase noise in fiber-optic systems employing a laser source with arbitrary coherence time,” J. Lightwave Technol. 4(9), 1334–1351 (1986). [CrossRef]

] with a loop length of 6.67 m. A 30 MHz FSR notch filter response was measured on a network analyser. Three significant taps were observed in the passive RDL notch filter impulse response. A high power single tone was applied to the phase modulator to obtain a large phase modulation index of 2.84 in order to obtain a large PIIN reduction. The PIIN at the RDL notch filter passband was measured for different frequency single tone into the phase modulator. Comparison between the experimental result and the theoretical prediction of the amount of the passive RDL PIIN reduction is shown in Fig. 7(a)
Fig. 7 (a) Measured and predicted amount of passive RDL notch filter PIIN reduction after different frequency single tone phase modulation. The phase modulation index is 2.84. (b) Measured and predicted amount of passive RDL notch filter PIIN reduction for different phase modulation indexes. The input single tone frequency is 2.9996 GHz.
. Close agreement between the measurement and the prediction can be seen. A 22 dB phase noise reduction was measured experimentally when the single tone frequency was tuned to 2.9996 GHz. It is interesting to note that the amount of phase noise reduction behaves periodically with the period equal to the FSR of the passive RDL notch filter response. Hence multiple solutions exist that provide the same amount of phase noise reduction. The single tone frequency was fixed at 2.9996 GHz. The amount of phase noise reduction at the passive RDL notch filter passband was measured for different phase modulation indexes as shown in Fig. 7(b).

An amplified RDL [1

1. B. Moslehi and J. W. Goodman, “Novel amplified fiber-optic recirculating delay line processor,” J. Lightwave Technol. 10(8), 1142–1147 (1992). [CrossRef]

], which can generate a large number of taps, was set up to investigate the phase noise reduction in a multi-tap delay line structure using the single tone phase modulation technique. The amplified RDL was formed by connecting one of the outputs of a 50% coupling ratio optical coupler back to one of its inputs. An erbium doped fibre amplifier was inserted into the amplified RDL loop to compensate for the loop loss. The amplifier gain was adjusted so that the first 20 taps in the amplified RDL impulse response had less than 20 dB reduction in amplitude compared to the first tap. This resulted in a bandpass filter response with a 25 dB rejection level, which was measured on a network analyser. The bandpass filter response had a FSR of 29.8 MHz. A 26.3 dBm high power single tone was applied to the phase modulator to obtain a large phase modulation index of 3.02 in order to obtain a large PIIN reduction. Figure 8(a)
Fig. 8 (a) Measured and predicted amount of amplified RDL bandpass filter PIIN reduction after different frequency single tone phase modulation. The phase modulation index is 3.02. (b) Measured and predicted amount of amplified RDL bandpass filter PIIN reduction for different phase modulation indexes. The input single tone frequency is 3.002 GHz.
shows the amount of PIIN reduction at the passband of the amplified RDL bandpass filter when the phase modulator was driven by different frequency single tones. This shows that the amount of phase noise reduction by single tone phase modulation in a 20-tap delay line signal processor is limited to 9.2 dB. However, unlike the UMZI and the passive RDL notch filters, the amount of phase noise reduction in the amplified RDL bandpass filter is not sensitive to the input single tone frequency. Figure 8(b) shows the measured and predicted amount of PIIN reduction at the amplified RDL bandpass filter passband for different phase modulation indexes while the single tone frequency was fixed at 3.002 GHz. Close agreements between the measured and simulated results can be seen. This verifies the validity of the model for predicting the amount of phase noise reduction in multi-tap delay line signal processing structures by using single tone phase modulation.

A pseudo-random binary sequence (PRBS) generated by a pattern generator instead of a single tone was used to investigate the changes in the delay line signal processor PIIN spectrum after broadening the laser linewidth. The spectrum width of the PRBS can be controlled by the clock frequency. The use of PRBS enables dynamic adjustment of the laser linewidth by simply changing the clock frequency. The narrow linewidth tuneable laser was intensity modulated by a quadrature biased EOM and was launched into a phase modulator driven by a high power PRBS. Initially the PRBS clock frequency was set to 75 MHz to broaden the laser linewidth to around 50 MHz to avoid the coherent interference effect in the delay line signal processor. The laser linewidth was measured by using the homodyne detection technique [19

19. M. Nazarathy, W. V. Sorin, D. M. Baney, and S. A. Newton, “Spectral analysis of optical mixing measurements,” J. Lightwave Technol. 7(7), 1083–1096 (1989). [CrossRef]

] when different clock frequency PRBSs were applied to the phase modulator. Then an UMZI notch filter was connected at the phase modulator output and the PIIN at the filter passband was measured for different PRBS clock frequency phase modulation. Comparison between the measured and predicted amount of PIIN reduction at the UMZI notch filter passband for different laser linewidth is depicted in Fig. 9
Fig. 9 Measured and predicted amount of UMZI notch filter PIIN reduction versus the laser linewidth.
. This shows that around 12 dB PIIN reduction was obtained by increasing the laser linewidth from 50 MHz to 920 MHz. The same amount of PIIN reduction was measured in the passive RDL notch filter and the amplified RDL bandpass filter. This shows a large PIIN reduction in multi-tap delay line signal processors can be obtained by broadening the laser linewidth.

To investigate the effect on the SNR, an RF signal having a frequency at the passband of the 30 MHz FSR passive RDL notch filter was applied to the intensity modulator. The output RF signal together with the passive RDL notch filter PIIN spectrum after broadening the tuneable laser linewidth from 50 MHz to 920 MHz are shown in Fig. 10
Fig. 10 RF signal and PIIN at the output of the passive RDL notch filter for the laser linewidth of 50 MHz (solid) and 920 MHz (dots). The FSR of the passive RDL notch filter response is 30 MHz.
. As seen phase modulation has no effect on the output RF signal. It only broadens the laser linewidth which distributes the PIIN into high frequencies. An 11.8 dB SNR improvement was obtained. A larger amount of SNR improvement can be obtained by further increasing the laser linewidth.

6. Conclusion

Acknowledgments

This work was supported by the Australian Research Council.

References and links

1.

B. Moslehi and J. W. Goodman, “Novel amplified fiber-optic recirculating delay line processor,” J. Lightwave Technol. 10(8), 1142–1147 (1992). [CrossRef]

2.

J. Capmany and J. Cascon, “Discrete time fiber-optic signal processors using optical amplifiers,” J. Lightwave Technol. 12(1), 106–117 (1994). [CrossRef]

3.

D. B. Hunter and R. A. Minasian, “Photonic signal processing of microwave signals using an active-fiber Bragg-grating-pair structure,” IEEE Trans. Microw. Theory Tech. 45(8), 1463–1466 (1997). [CrossRef]

4.

E. H. W. Chan, K. E. Alameh, and R. A. Minasian, “Photonic bandpass filters with high skirt selectivity and stopband attenuation,” J. Lightwave Technol. 20(11), 1962–1967 (2002). [CrossRef]

5.

G. Yu, W. Zhang, and J. A. R. Williams, “High-performance microwave transversal filter using fiber Bragg grating arrays,” IEEE Photon. Technol. Lett. 12(9), 1183–1185 (2000). [CrossRef]

6.

D. B. Hunter and R. A. Minasian, “Tunable microwave fiber-optic bandpass filters,” IEEE Photon. Technol. Lett. 11(7), 874–876 (1999). [CrossRef]

7.

D. Pastor, S. Sales, J. Capmany, J. Marti, and J. Cascon, “Amplified double coupler fiber-optic delay line filter,” IEEE Photon. Technol. Lett. 7(1), 75–77 (1995). [CrossRef]

8.

E. H. W. Chan and R. A. Minasian, “Reflective amplified recirculating delay line bandpass filter,” J. Lightwave Technol. 25(6), 1441–1446 (2007). [CrossRef]

9.

J. Capmany, B. Ortega, D. Pastor, and S. Sales, “Discrete-time optical processing of microwave signals,” J. Lightwave Technol. 23(2), 702–723 (2005). [CrossRef]

10.

M. Y. Frankel and R. D. Esman, “Fiber-optic tunable microwave transversal filter,” IEEE Photon. Technol. Lett. 7(2), 191–193 (1995). [CrossRef]

11.

M. Tur and A. Arie, “Phase induced intensity noise in concatenated fiber-optic delay lines,” J. Lightwave Technol. 6(1), 120–130 (1988). [CrossRef]

12.

B. Moslehi, “Analysis of optical phase noise in fiber-optic systems employing a laser source with arbitrary coherence time,” J. Lightwave Technol. 4(9), 1334–1351 (1986). [CrossRef]

13.

J. T. Kringlebotn and K. Blotekjaer, “Noise analysis of an amplified fiber-optic recirculating delay line,” J. Lightwave Technol. 12(3), 573–582 (1994). [CrossRef]

14.

E. H. W. Chan and R. A. Minasian, “Suppression of phase induced intensity noise in optical delay line signal processors using a differential detection technique,” IEEE Trans. Microw. Theory Tech. 54(2), 873–879 (2006). [CrossRef]

15.

A. Yariv, H. Blauvelt, D. Huff, and H. Zarem, “An experimental and theoretical study of the suppression of interferometric noise and distortion in AM optical links by phase dither,” J. Lightwave Technol. 15(3), 437–443 (1997). [CrossRef]

16.

P. K. Pepeljugoski and K. Y. Lau, “Interferometric noise reduction in fiber-optic links by superposition of high frequency modulation,” J. Lightwave Technol. 10(7), 957–963 (1992). [CrossRef]

17.

A. H. Quoc and S. Tedjini, “Experimental investigation on the optical unbalanced Mach-Zehnder interferometers as microwave filters,” IEEE Microwave Guided Wave Lett. 4(6), 183–185 (1994). [CrossRef]

18.

E. H. W. Chan and R. A. Minasian, “Optical source coherence controller for fibre optic delay line RF/microwave signal processors,” Opt. Commun. 254(1-3), 104–111 (2005). [CrossRef]

19.

M. Nazarathy, W. V. Sorin, D. M. Baney, and S. A. Newton, “Spectral analysis of optical mixing measurements,” J. Lightwave Technol. 7(7), 1083–1096 (1989). [CrossRef]

OCIS Codes
(060.2360) Fiber optics and optical communications : Fiber optics links and subsystems
(350.4010) Other areas of optics : Microwaves
(070.2025) Fourier optics and signal processing : Discrete optical signal processing
(070.2615) Fourier optics and signal processing : Frequency filtering

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: July 21, 2010
Revised Manuscript: September 16, 2010
Manuscript Accepted: September 16, 2010
Published: September 27, 2010

Citation
Erwin H. W. Chan, "Suppression of phase-induced intensity noise in fibre optic delay line signal processors using an optical phase modulation technique," Opt. Express 18, 21573-21584 (2010)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-21-21573


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References

  1. B. Moslehi and J. W. Goodman, “Novel amplified fiber-optic recirculating delay line processor,” J. Lightwave Technol. 10(8), 1142–1147 (1992). [CrossRef]
  2. J. Capmany and J. Cascon, “Discrete time fiber-optic signal processors using optical amplifiers,” J. Lightwave Technol. 12(1), 106–117 (1994). [CrossRef]
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