Camatel, S.

Ferrero, Valter

English

CAMATEL S

FERRERO, Valter

PORTO@iris (Publications Open Repository TOrino - Politecnico di Torino)

05 August 2020POLITECNICO DI TORINORepository ISTITUZIONALEPhase Noise Power Spectral Density Measurement of Narrow Linewidth CW Lasers Using an Optical Phase-LockedLoop / CAMATEL S; FERRERO V.. - In: IEEE PHOTONICS TECHNOLOGY LETTERS. - ISSN 1041-1135. - STAMPA. -Volume 18:Issue 23(2006), pp. 2529-2531.OriginalPhase Noise Power Spectral Density Measurement of Narrow Linewidth CW Lasers Using an OpticalPhase-Locked LoopPublisher:PublishedDOI:10.1109/LPT.2006.887206Terms of use:openAccessPublisher copyright(Article begins on next page)This article is made available under terms and conditions as specified in the  corresponding bibliographic description inthe repositoryAvailability:This version is available at: 11583/1534758 since:IEEEIEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 18, NO. 23, DECEMBER 1, 2006 2529Phase Noise Power Spectral Density Measurementof Narrow Linewidth CW Lasers Usingan Optical Phase-Locked LoopStefano Camatel, Member, IEEE, and Valter Ferrero, Member, IEEEAbstract—A novel technique for continuous-wave (CW) laserphase noise power spectral density measurement, useful forcoherent communications, is proposed. It employs a homodyneoptical phase-locked loop. Experimental results are comparedwith a self-heterodyne linewidth measurement and the compar-ison shows how the proposed measurement method gives moreaccurate results for coherent transmission system applications.Index Terms—Homodyne detection, phase-locked loops, phasemeasurement, phase noise.I. INTRODUCTIONRECEIVER sensitivity limit in coherent optical communi-cations is mainly affected by semiconductor laser phasefluctuations [1], [2]. Also, sensors based on optical fiber inter-ferometer systems have a sensitivity limited by phase noise [3].For these reasons, many works focused on phase noise charac-teristics of semiconductor lasers have been published [4], [5].Measurement methods for laser linewidth characterization wereproposed in the past years; most of them are based on interfer-ometric techniques [6], [7].Here, we propose an accurate measurement technique ade-quate for testing lasers to be used in optical coherent commu-nications. Such a method is able to retrieve the power spectraldensity (PSD) of the overall phase noise produced by two lasers,a source laser and a local oscillator (LO) laser. The combinedphase noise can then be used for the design and performance es-timation of a coherent transmission system. By the way, the CWsource laser phase noise PSD could be obtained by this method,if the used LO laser is affected by a negligible phase noise.Our measurement technique is based on an optical phase-lockedloop (OPLL) which can be described by a linear model. In thisletter, we show experimental results obtained by using an OPLLbased on sub-carrier modulation (SC-OPLL) [8]. This way, weare able to characterize CW lasers phase noise; optical oscilla-tors with direct frequency modulation are not required.Experimental results are also presented in this letter and com-pared with a common delayed self-heterodyne method.Manuscript received August 7, 2006; revised October 11, 2006. This workwas supported in part by the EU FP6 Network of Excellence e-Photon/ONe,WP5 and WP10.S. Camatel is with PhotonLab, Istituto Superiore Mario Boella, 10138 Torino,Italy (e-mail: camatel@ismb.it).V. Ferrero is with PhotonLab, Dipartimento di Elettronica, Politecnico diTorino, 10129 Torino, Italy (e-mail: valter.ferrero@polito.it).Digital Object Identifier 10.1109/LPT.2006.887206Fig. 1. Setup for measurement of the phase error signal spectrum (a) and theOPLL frequency response (b).II. MEASUREMENT METHODThe operation principle is based on a linear OPLL [seeFig. 1(a)] that can be described by a linearized model. Anexhaustive study of such a model was presented in [1] andwill be used as the starting point of the following treatment.The source laser is not modulated and the phase-lock to datacrosstalk will not be taken into account. The signal powerlevel at the OPLL input is set, in order to have shot noise andamplitude electrical noises negligible. This way, the overallphase noise of the source and local oscillator lasers is the onlycontribution that will be considered. The fundamental equationthat allows evaluating the phase noise PSD is(1)where is the Fourier transform of the phase error signal,is a constant coefficient, is the phase noise Fouriertransform, and is the PLL closed-loop transfer func-tion. , as defined in [1], depends on photodiode respon-sivity, transimpedance gain, received signal and local oscillatorpowers. In the experimental setup, shown in Fig. 1(a), the spec-trum analyzer measures the spectrum of the phaseerror signal, which can be expressed as(2)1041-1135/$20.00 © 2006 IEEE2530 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 18, NO. 23, DECEMBER 1, 2006where is the sum of the PSD of the lasers’ phase noise,and is the spectrum analyzer resolution bandwidth. The PLLtransfer function and the constant can be measured in theexperimental setup of Fig. 1(b), where the network analyzer re-turns the following response:(3)In (3), is the voltage that has to be applied to the phase modu-lator in order to get a phase deviation of radians. The functioncan be evaluated from (3) and substitutedin (2), giving as result the following formula:(4)Equation (4) returns the PSD of the phase noise lasers giventhe measurement results obtained by the experiments shown inFig. 1.III. EXPERIMENTAL RESULTSThe previously described technique was implemented forthe characterization of two couples of external cavity tunablelasers. The first couple includes two Agilent 81640A, while thesecond couple consists of two Anritsu MG9638A. Declaredlinewidths are lower than 100 kHz for the Agilent model, and700 kHz for the Anritsu model. The OPLL employed for phasenoise measurement is an SC-OPLL [8]. The signal power at thephotodiode input was set to 16 dBm, while the overall LOpower was 3 dBm. The photodiode has responsivity equalto 800 V/W. The optical voltage controlled oscillator (VCO)includes a 10-GHz LiNbO intensity modulator and a 6-GHzelectrical VCO. The loop filter is a first-order active filter,whose time constants are s and s. Suchtime constants were chosen in order to get a second-order PLLtransfer function with natural frequency kHz anddamping factor .The value of kHz is the lowest natural fre-quency that allows OPLL locking, thus it affects the evaluationof for low-frequency values. At high frequencies,is limited by additive white Gaussian noise. At lowfrequencies, is not accurate due to the limited networkanalyzer sensitivity. Thus, our measurement method is only ac-curate in a limited frequency range around . The upper limitcould be overcome by repeating the measurement procedure forhigher OPLL natural frequencies. Anyway, the highest OPLLnatural frequency that can be set depends on the OPLL loopdelay. Our SC-OPLL was affected by a 15-ns feedback loopdelay and 8 MHz is the maximum natural frequency for whichSC-OPLL can still lock (see [8]). By the way, we were ableto measure and estimate on an acceptablerange, so we performed the proposed measurement just withkHz.The measurement setups shown in Fig. 1 were performed.The electrical spectrum analyzer of Fig. 1(a) was set with a res-olution bandwidth equal to 1 kHz and a video bandwidth ofFig. 2. Measured phase noise PSD of Agilent 81640A (top) and AnritsuMG9638A (bottom) lasers. A theoretical PSD with a linewidth of 9.5 kHz issuperimposed.100 Hz. The network analyzer of Fig. 1(b) generates a signalof 4 dBm and drives a LiNbO phase modulator with. As previously anticipated, the measurements ofand allowed the phase noise PSD evaluation of twoAgilent 81640A and two Anritsu MG9638A external cavity tun-able lasers. Fig. 2 shows measurement results.An ideal phase noise PSD is also plotted in Fig. 2, and it wasobtained by considering the combination of two identical whitefrequency noises, whose one-sided PSD is given by(5)where kHz is the laser linewidth that best fits themeasured PSD of Agilent 81640A. The same curve is depictedin the lower part of Fig. 2 and compared with the PSD esti-mate of Anritsu MG9638A. Fig. 2 shows how the first PSD fol-lows the ideal curve and on the measurement frequency rangeAgilent 81640 is approximately characterized by a white fre-quency noise. In contrast, the phase noise PSD curve of theAnritsu MG9638A deviates from ideal white frequency noisecurve, and is steeper at low frequencies. This suggests worsephase noise performance. To correctly model the behavior of theAnritsu laser, the phase noise contributions—which mayarise from flicker noise or random-walk noise—have to be con-sidered [2].CAMATEL AND FERRERO: PHASE NOISE POWER SPECTRAL DENSITY MEASUREMENT OF NARROW LINEWIDTH CW LASERS 2531Fig. 3. Delayed self-heterodyne measurement results for Agilent 81640A(top) and Anritsu MG9638A (bottom) lasers, which show respectively = FWHM=2 = 175 kHz and  = 600 kHz.We calculated the in-band phase noise contributions willincrease the phase error standard deviation by 10% with respectto the ideal Lorentzian lineshape, when the natural frequency isset to 3 MHz.Both source and local oscillator lasers were characterized bya delayed self-heterodyne measurement technique [9]. Such ameasurement setup included a 20-km spoon fiber as delay lineand an acoustooptic modulator with 27-MHz frequency shift.Fig. 3 shows the detected spectrum, which reveals a linewidthof almost 175 kHz for the Agilent laser and 600 kHz for theAnritsu laser. Such results confirm the worse performance interms of phase noise of Anritsu lasers.The considered measurement techniques gave differentresults. This fact was just observed in [6] during the charac-terization of DFB lasers and is due to an overestimation ofthe linewidth when the self-heterodyne method has to dealwith deviations of the laser lineshape from the Lorentzianshape, i.e. when the frequency noise spectrum is no longer aflat spectrum because of terms. Such contributionscorrespond to optical frequency instability and usually havevery low speed variation. From an empirical point of view, itcan be explained by a frequency shifting, varying with time,of a perfect Lorentzian shape (see Fig. 4). The self-heterodyne(or also self-homodyne) method, being a low-speed measure-ment, is able to measure only the envelope of the frequencyFig. 4. Instantaneous shots of the drifting Lorentzian spectrum (straight lines)varying with time and long term spectrum (dotted) obtained by a protractedobservation.drifting “perfect” Lorentzian source (see Fig. 4). Since ourmeasurement technique analyzes phase noise contributionson a limited frequency range, it does not take into accountcontributions at frequencies much lower than the OPLLnatural frequency . Such low-frequency contributions are notignored in the self-heterodyne measurement. Anyway, they donot affect performance in coherent systems applications, sothey do not have to be considered in laser phase noise experi-mental characterizations. For this reason, our method is morereliable for coherent communications because it estimates the“correct” amount of noise that affects the performance. Theother mentioned methods overestimate the amount of phasenoise for coherent applications.IV. CONCLUSIONA novel measurement technique for the acquisition of thecombined PSD of two lasers was presented. It is able to eval-uate the phase noise on a part of the spectrum that determines theinfluence of linewidth on coherent systems. Other approaches,such as delayed self-heterodyne, give a pessimistic estimationof the linewidth. Therefore, the proposed technique gives themost useful value for linewidth to be used in the performanceevaluation and design of coherent optical transmission systems.REFERENCES[1] L. G. Kazovsky, “Balanced phase-locked loops for optical homodynereceivers: performance analysis, design considerations, and laserlinewidth requirements,” J. Lightw. Technol., vol. LT-4, no. 2, pp.182–195, Feb. 1986.[2] S. Norimatsu and O. Ishida, “Impact of flicker noise and random-walknoise on a phase-locked loop with finite propagation delay,” J. Lightw.Technol., vol. 12, no. 1, pp. 86–95, Jan. 1994.[3] A. Dandridge and A. B. Tveten, “Phase noise of single-mode diodelasers in interferometer systems,” Appl. Phys. Lett., vol. 39, p. 530,1981.[4] B. Daino, P. Spano, M. Tamburrini, and S. Piazzolla, “Phase noise andspectral line shape in semiconductor lasers,” IEEE J. Quantum Elec-tron., vol. QE-19, no. 3, pp. 266–270, Mar. 1983.[5] C. H. Henry, “Phase noise in semiconductor lasers,” J. Lightw.Technol., vol. LT-4, no. 3, pp. 298–311, Mar. 1986.[6] M. O. Van Deventer, P. Spano, and S. K. Nielsen, “Comparison of DFBlaser linewidth measurement techniques results from COST 215 roundrobin,” Electron. Lett., vol. 26, no. 24, pp. 2018–2020, Nov. 22, 1990.[7] T. Okoshi and K. Kikuchi, Coherent Optical Fiber Communications.New York: Kluwer, 1988.[8] S. Camatel, V. Ferrero, R. Gaudino, and P. Poggiolini, “Optical phase-locked loop for coherent detection optical receiver,” Electron. Lett., vol.40, no. 6, pp. 384–385, Mar. 18, 2004.[9] T. Okoshi, K. Kikuchi, and A. Nakayama, “Novel method for highresolution measurement of laser output spectrum,” Electron. Lett., vol.16, p. 630, 1980.

Phase Noise Power Spectral Density Measurement of Narrow Linewidth CW Lasers Using an Optical Phase-Locked Loop

PORTO Publications Open Repository TOrino

IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 18, NO. 23, DECEMBER 1, 2006 2529
Phase Noise Power Spectral Density Measurement
of Narrow Linewidth CW Lasers Using
an Optical Phase-Locked Loop
Stefano Camatel, Member, IEEE, and Valter Ferrero, Member, IEEE
Abstract—A novel technique for continuous-wave (CW) laser
phase noise power spectral density measurement, useful for
coherent communications, is proposed. It employs a homodyne
optical phase-locked loop. Experimental results are compared
with a self-heterodyne linewidth measurement and the compar-
ison shows how the proposed measurement method gives more
accurate results for coherent transmission system applications.
Index Terms—Homodyne detection, phase-locked loops, phase
measurement, phase noise.
I. INTRODUCTION
RECEIVER sensitivity limit in coherent optical communi-cations is mainly affected by semiconductor laser phase
fluctuations [1], [2]. Also, sensors based on optical fiber inter-
ferometer systems have a sensitivity limited by phase noise [3].
For these reasons, many works focused on phase noise charac-
teristics of semiconductor lasers have been published [4], [5].
Measurement methods for laser linewidth characterization were
proposed in the past years; most of them are based on interfer-
ometric techniques [6], [7].
Here, we propose an accurate measurement technique ade-
quate for testing lasers to be used in optical coherent commu-
nications. Such a method is able to retrieve the power spectral
density (PSD) of the overall phase noise produced by two lasers,
a source laser and a local oscillator (LO) laser. The combined
phase noise can then be used for the design and performance es-
timation of a coherent transmission system. By the way, the CW
source laser phase noise PSD could be obtained by this method,
if the used LO laser is affected by a negligible phase noise.
Our measurement technique is based on an optical phase-locked
loop (OPLL) which can be described by a linear model. In this
letter, we show experimental results obtained by using an OPLL
based on sub-carrier modulation (SC-OPLL) [8]. This way, we
are able to characterize CW lasers phase noise; optical oscilla-
tors with direct frequency modulation are not required.
Experimental results are also presented in this letter and com-
pared with a common delayed self-heterodyne method.
Manuscript received August 7, 2006; revised October 11, 2006. This work
was supported in part by the EU FP6 Network of Excellence e-Photon/ONe,
WP5 and WP10.
S. Camatel is with PhotonLab, Istituto Superiore Mario Boella, 10138 Torino,
Italy (e-mail: camatel@ismb.it).
V. Ferrero is with PhotonLab, Dipartimento di Elettronica, Politecnico di
Torino, 10129 Torino, Italy (e-mail: valter.ferrero@polito.it).
Digital Object Identifier 10.1109/LPT.2006.887206
Fig. 1. Setup for measurement of the phase error signal spectrum (a) and the
OPLL frequency response (b).
II. MEASUREMENT METHOD
The operation principle is based on a linear OPLL [see
Fig. 1(a)] that can be described by a linearized model. An
exhaustive study of such a model was presented in [1] and
will be used as the starting point of the following treatment.
The source laser is not modulated and the phase-lock to data
crosstalk will not be taken into account. The signal power
level at the OPLL input is set, in order to have shot noise and
amplitude electrical noises negligible. This way, the overall
phase noise of the source and local oscillator lasers is the only
contribution that will be considered. The fundamental equation
that allows evaluating the phase noise PSD is
(1)
where is the Fourier transform of the phase error signal,
is a constant coefficient, is the phase noise Fourier
transform, and is the PLL closed-loop transfer func-
tion. , as defined in [1], depends on photodiode respon-
sivity, transimpedance gain, received signal and local oscillator
powers. In the experimental setup, shown in Fig. 1(a), the spec-
trum analyzer measures the spectrum of the phase
error signal, which can be expressed as
(2)
1041-1135/$20.00 © 2006 IEEE
2530 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 18, NO. 23, DECEMBER 1, 2006
where is the sum of the PSD of the lasers’ phase noise,
and is the spectrum analyzer resolution bandwidth. The PLL
transfer function and the constant can be measured in the
experimental setup of Fig. 1(b), where the network analyzer re-
turns the following response:
(3)
In (3), is the voltage that has to be applied to the phase modu-
lator in order to get a phase deviation of radians. The function
can be evaluated from (3) and substituted
in (2), giving as result the following formula:
(4)
Equation (4) returns the PSD of the phase noise lasers given
the measurement results obtained by the experiments shown in
Fig. 1.
III. EXPERIMENTAL RESULTS
The previously described technique was implemented for
the characterization of two couples of external cavity tunable
lasers. The first couple includes two Agilent 81640A, while the
second couple consists of two Anritsu MG9638A. Declared
linewidths are lower than 100 kHz for the Agilent model, and
700 kHz for the Anritsu model. The OPLL employed for phase
noise measurement is an SC-OPLL [8]. The signal power at the
photodiode input was set to 16 dBm, while the overall LO
power was 3 dBm. The photodiode has responsivity equal
to 800 V/W. The optical voltage controlled oscillator (VCO)
includes a 10-GHz LiNbO intensity modulator and a 6-GHz
electrical VCO. The loop filter is a first-order active filter,
whose time constants are s and s. Such
time constants were chosen in order to get a second-order PLL
transfer function with natural frequency kHz and
damping factor .
The value of kHz is the lowest natural fre-
quency that allows OPLL locking, thus it affects the evaluation
of for low-frequency values. At high frequencies,
is limited by additive white Gaussian noise. At low
frequencies, is not accurate due to the limited network
analyzer sensitivity. Thus, our measurement method is only ac-
curate in a limited frequency range around . The upper limit
could be overcome by repeating the measurement procedure for
higher OPLL natural frequencies. Anyway, the highest OPLL
natural frequency that can be set depends on the OPLL loop
delay. Our SC-OPLL was affected by a 15-ns feedback loop
delay and 8 MHz is the maximum natural frequency for which
SC-OPLL can still lock (see [8]). By the way, we were able
to measure and estimate on an acceptable
range, so we performed the proposed measurement just with
kHz.
The measurement setups shown in Fig. 1 were performed.
The electrical spectrum analyzer of Fig. 1(a) was set with a res-
olution bandwidth equal to 1 kHz and a video bandwidth of
Fig. 2. Measured phase noise PSD of Agilent 81640A (top) and Anritsu
MG9638A (bottom) lasers. A theoretical PSD with a linewidth of 9.5 kHz is
superimposed.
100 Hz. The network analyzer of Fig. 1(b) generates a signal
of 4 dBm and drives a LiNbO phase modulator with
. As previously anticipated, the measurements of
and allowed the phase noise PSD evaluation of two
Agilent 81640A and two Anritsu MG9638A external cavity tun-
able lasers. Fig. 2 shows measurement results.
An ideal phase noise PSD is also plotted in Fig. 2, and it was
obtained by considering the combination of two identical white
frequency noises, whose one-sided PSD is given by
(5)
where kHz is the laser linewidth that best fits the
measured PSD of Agilent 81640A. The same curve is depicted
in the lower part of Fig. 2 and compared with the PSD esti-
mate of Anritsu MG9638A. Fig. 2 shows how the first PSD fol-
lows the ideal curve and on the measurement frequency range
Agilent 81640 is approximately characterized by a white fre-
quency noise. In contrast, the phase noise PSD curve of the
Anritsu MG9638A deviates from ideal white frequency noise
curve, and is steeper at low frequencies. This suggests worse
phase noise performance. To correctly model the behavior of the
Anritsu laser, the phase noise contributions—which may
arise from flicker noise or random-walk noise—have to be con-
sidered [2].
CAMATEL AND FERRERO: PHASE NOISE POWER SPECTRAL DENSITY MEASUREMENT OF NARROW LINEWIDTH CW LASERS 2531
Fig. 3. Delayed self-heterodyne measurement results for Agilent 81640A
(top) and Anritsu MG9638A (bottom) lasers, which show respectively
 = FWHM=2 = 175 kHz and  = 600 kHz.
We calculated the in-band phase noise contributions will
increase the phase error standard deviation by 10% with respect
to the ideal Lorentzian lineshape, when the natural frequency is
set to 3 MHz.
Both source and local oscillator lasers were characterized by
a delayed self-heterodyne measurement technique [9]. Such a
measurement setup included a 20-km spoon fiber as delay line
and an acoustooptic modulator with 27-MHz frequency shift.
Fig. 3 shows the detected spectrum, which reveals a linewidth
of almost 175 kHz for the Agilent laser and 600 kHz for the
Anritsu laser. Such results confirm the worse performance in
terms of phase noise of Anritsu lasers.
The considered measurement techniques gave different
results. This fact was just observed in [6] during the charac-
terization of DFB lasers and is due to an overestimation of
the linewidth when the self-heterodyne method has to deal
with deviations of the laser lineshape from the Lorentzian
shape, i.e. when the frequency noise spectrum is no longer a
flat spectrum because of terms. Such contributions
correspond to optical frequency instability and usually have
very low speed variation. From an empirical point of view, it
can be explained by a frequency shifting, varying with time,
of a perfect Lorentzian shape (see Fig. 4). The self-heterodyne
(or also self-homodyne) method, being a low-speed measure-
ment, is able to measure only the envelope of the frequency
Fig. 4. Instantaneous shots of the drifting Lorentzian spectrum (straight lines)
varying with time and long term spectrum (dotted) obtained by a protracted
observation.
drifting “perfect” Lorentzian source (see Fig. 4). Since our
measurement technique analyzes phase noise contributions
on a limited frequency range, it does not take into account
contributions at frequencies much lower than the OPLL
natural frequency . Such low-frequency contributions are not
ignored in the self-heterodyne measurement. Anyway, they do
not affect performance in coherent systems applications, so
they do not have to be considered in laser phase noise experi-
mental characterizations. For this reason, our method is more
reliable for coherent communications because it estimates the
“correct” amount of noise that affects the performance. The
other mentioned methods overestimate the amount of phase
noise for coherent applications.
IV. CONCLUSION
A novel measurement technique for the acquisition of the
combined PSD of two lasers was presented. It is able to eval-
uate the phase noise on a part of the spectrum that determines the
influence of linewidth on coherent systems. Other approaches,
such as delayed self-heterodyne, give a pessimistic estimation
of the linewidth. Therefore, the proposed technique gives the
most useful value for linewidth to be used in the performance
evaluation and design of coherent optical transmission systems.
REFERENCES
[1] L. G. Kazovsky, “Balanced phase-locked loops for optical homodyne
receivers: performance analysis, design considerations, and laser
linewidth requirements,” J. Lightw. Technol., vol. LT-4, no. 2, pp.
182–195, Feb. 1986.
[2] S. Norimatsu and O. Ishida, “Impact of flicker noise and random-walk
noise on a phase-locked loop with finite propagation delay,” J. Lightw.
Technol., vol. 12, no. 1, pp. 86–95, Jan. 1994.
[3] A. Dandridge and A. B. Tveten, “Phase noise of single-mode diode
lasers in interferometer systems,” Appl. Phys. Lett., vol. 39, p. 530,
1981.
[4] B. Daino, P. Spano, M. Tamburrini, and S. Piazzolla, “Phase noise and
spectral line shape in semiconductor lasers,” IEEE J. Quantum Elec-
tron., vol. QE-19, no. 3, pp. 266–270, Mar. 1983.
[5] C. H. Henry, “Phase noise in semiconductor lasers,” J. Lightw.
Technol., vol. LT-4, no. 3, pp. 298–311, Mar. 1986.
[6] M. O. Van Deventer, P. Spano, and S. K. Nielsen, “Comparison of DFB
laser linewidth measurement techniques results from COST 215 round
robin,” Electron. Lett., vol. 26, no. 24, pp. 2018–2020, Nov. 22, 1990.
[7] T. Okoshi and K. Kikuchi, Coherent Optical Fiber Communications.
New York: Kluwer, 1988.
[8] S. Camatel, V. Ferrero, R. Gaudino, and P. Poggiolini, “Optical phase-
locked loop for coherent detection optical receiver,” Electron. Lett., vol.
40, no. 6, pp. 384–385, Mar. 18, 2004.
[9] T. Okoshi, K. Kikuchi, and A. Nakayama, “Novel method for high
resolution measurement of laser output spectrum,” Electron. Lett., vol.
16, p. 630, 1980.


Balanced phase-locked loops for optical homodyne receivers: performance analysis, design considerations, and laser linewidth requirements,”

Impact of ﬂicker noise and random-walk noise on a phase-locked loop with ﬁnite propagation delay,”

M.O.VanDeventer,P.Spano,andS.K.Nielsen,“ComparisonofDFB laser linewidth measurement techniques results from COST 215 round robin,”

Phase Noise Power Spectral Density Measurement of Narrow Linewidth CW Lasers Using an Optical Phase-Locked Loop

Abstract

Similar works

Full text

Available Versions

PORTO@iris (Publications Open Repository TOrino - Politecnico di Torino)

PORTO Publications Open Repository TOrino