Multi-wavelength Semiconductor Fiber Lasers

5/19/2006CIPI Workshop on Fiber LasersL R Chen

Multi-wavelength Semiconductor Fiber Lasers

Lawrence R. ChenPhotonic Systems Group

Department of Electrical and Computer EngineeringMcGill University

Montreal, Quebec, [email protected]


Acknowledgments

• Reuven E. Gordon, Véronique Pagé, Dr. Varghese Baby

• Serge Doucet, Prof. Sophie LaRochelle

• NSERC Canada and Canadian Institute for Photonic Innovations

• Anritsu Electronics, Ltd.


• Multi-wavelength optical sources have numerous applications:– Optical instrumentation– Fiber optic sensing– Optical communications– Microwave photonics

• Regimes of operation– Continuous wave– Mode-locked

• Fiber-based solutions are attractive and have the advantage of low coupling loss to optical fiber systems

Motivation


• Stable operation– Power– Wavelength

• Broad wavelength range• Wavelength spacing from very large (100’s of GHz) to very

narrow (10’s of GHz)• High output power (mW)• Single longitudinal mode• Tunable operation

Features


• Stable, multi-wavelength operation with narrow wavelength spacing is difficult to achieve in erbium-doped fiber (EDF) due to homogeneous broadening– Cool to 77 K– Frequency-shifting– Polarization holeburning– Careful gain equalization – Complex cavities

• Semiconductor optical amplifiers exhibit inhomogeneous linewidth broadening

Challenges


• Use SOAs as the gain medium

• Ring or standing-wave cavities

• Multi-wavelength filters– Ideally, fiber-based such as:

Fiber Bragg gratings Mach-Zehnder interferometers

• Tunable multi-wavelength operation– Tunable wavelength filters (lasing wavelengths are

individually tunable)– Tunable comb filters (lasing wavelengths have equally

increased or decreased wavelength spacing)

Semiconductor Fiber Lasers


• First demonstration of a multi-wavelength semiconductor fiber ring laser– Serial SOAs used to increase lasing bandwidth

SFL with a Fabry-Pérot Filter

N. Pleros et al, IEEE PTL, vol. 14, pp. 693-695 (2002)

38 wavelengths with 50 GHz channel spacing


• First demonstration of multi-wavelength lasing in a ring laser using a sampled FBG

SFL with Sampled FBG

J. Sun et al, IEEE PTL, vol. 14, pp. 750-752 (2002)

nP2

2

Sampled FBG: periodic comb filterwith wavelength spacing set by thesample period P


• Switchable operation demonstrated with a sampled FBG in HiBi fiber

SFL with Sampled FBG in HiBi Fiber

B.-A. Yu et al, IEE EL, vol. 39, pp. 649-650 (2003)

yx nn 2

Due to the different effective indices of the x and y polarizations in the HiBi fiber, each polarization will have its own reflection peak


• > 40 wavelengths with 0.5 nm spacing and tunable operation– VOA used to control lasing wavelengths by saturating

the SOA

SFL with a Mach-Zehnder Interferometer

F. W. Tong et al, IEE EL, vol. 40, pp. 594-595 (2004)

VOA = 3 dB

, nm, nm

VOA = 8.5 dBVOA = 14 dB

, nm


• 75 wavelengths with 40 GHz spacing

SFL with a PLC-BasedDelayed Interferometer

DI spectral responseLaser output

increasingcavityloss

H. Dong et al, IEEE PTL, vol. 17, pp. 303-305 (2005)


• 50 wavelengths with 50 GHz spacing at 1300 nm

SFL with a Fabry-Pérot Filter

H. Chen, Opt Lett, vol. 30, pp. 619-621 (2005)


• LOA (gain-clamped SOA)– Reduced transients compared to conventional SOA

which results in improved power stability

SFL with a Linear Optical Amplifier

K. K. Kureshi, IEEE PTL, vol. 17, pp. 1611-1613 (2005)


• 20 wavelengths with 100 GHz spacing using multi-wavelength thin film etalon filter


Sample laser output


• Comparison of power stability


LOA SOA


• Fiber loop mirror incorporating a segment of HiBi fiber– Coupler splits input beam into two counter-propagating

beams and recombines them after traveling through fiber loop

– Birefringence (n) produces a phase difference () between the fast and slow components of a propagating beam

HiBi Fiber Loop Mirror Comb Filter

Fang and Claus, Opt Lett, vol. 20, pp. 2146-2148 (1995)Dong et al., Electron. Lett., vol. 36, pp. 1609-1610 (2000)

PC1

HiBi, L

3 dBcoupler

in

out

• Reflectivity of FLM depends on this phase difference:

where • Periodicity given by

cos121

)( R

/2 nL

nL

2


• Interleaved waveband switching• 17 wavelengths with 100 GHz spacing, bands separated

by 50 GHz

SFL with HiBi-FLM

Y. W. Lee et al, IEEE PTL, vol. 16, pp. 54-56 (2004)

Comb filter responseLaser output response


Digitally Programmable HiBi-FLM

L. R. Chen, IEEE PTL, vol. 16, pp. 410-412 (2004)

• State of the switches determines the total length of HiBi fiber in the FLM– If the HiBi fiber segments have equal lengths L, the

total length can be varied digitally between L, 2L, … NL– Thus, the wavelength separation can also vary digitally

between

…

PC1

HiBi, L1

PC2

HiBi, L2

PCN

HiBi, LN

22 switch3 dBcoupler

combinerin

out

nLNnLnL

222

,,2

,

• As a simple demonstration, we use two fiber segments and one switch– For the cross-state,

– For the bar state,

PC1

HiBi, LPC2

HiBi, L

22 switch3 dBcoupler

combinerin

out

nL

2

nL

2

2


Digitally Programmable HiBi-FLM

1535 1540 1545 1550 1555 1560 1565-60

-40

-20

contrast > 20 dB = 3.2 nm

Ref

lect

ivity

, dB

Wavelength, nm

Switch in cross-state• L = 1.99 m 3.2 nm• insertion loss 7 dB

1535 1540 1545 1550 1555 1560 1565-90

-80

-70

-60

-50

contrast > 15 dB = 1.6 nm

Ref

lect

ivity

, dB

Wavelength, nm

Switch in bar state• L = 3.98 m 1.6 nm• insertion loss 10 dB

After changing the state of theswitch, may need to adjust PC to optimize contrast

• Results


1540 1550 1560 1570 1580 1590 1600-80

-70

-60

-50

-40

-30

-20

-10

P = < 5 dB

Out

put p

ower

, dB

m

Wavelength, nm

Tunable SFL

• Switch in cross-state

• 6 lasing wavelengths with minimum SNR = 40 dB• linewidths < 0.12 nm

• Switch in bar-state

• 11 lasing wavelengths with minimum SNR = 36 dB• linewidths < 0.15 nm

1540 1550 1560 1570 1580 1590 1600-80

-70

-60

-50

-40

-30

-20

-10

P = < 8.5 dB

Out

put p

ower

, dB

m

Wavelength, nm


1562 1564 1566 1568 1570 1572

Wavelength, nmin

tens

ity, 1

0 dB

/div

Tunable SFL

• Stability: repeated scans of output spectra

Output power fluctuations < 1.5 dBWavelength variations < 0.05 nm

1560 1565 1570 1575 1580

Wavelength, nm

inte

nsity

, 10

dB/d

iv

Switch in cross-state ( = 3.2 nm) Switch in bar state ( = 1.6 nm)


Waveband-Switchable SFL

M. P. Fok et al, IEEE PTL, vol. 17, pp. 1393-1395 (2005)

• Phase modulator in HiBi-FLM allows tuning of the comb filter transfer function– Used to vary amount of birefringence in the loop– Shift in comb response but comb spacing is unchanged



• Increased wavelength range of operation

SFL with HiBi-FLMand Hybrid SOA-EDFA Gain Medium

Y.-G. Han et al, IEEE PTL, vol. 17, pp. 989-991 (2005)

Tunable wavelength spacingTunable wavelengths


• Superimposed chirped FBGs can be used to create a high-finesse FP resonator (CFPR)

FBG-Based Fabry-Pérot

R. Slavík et al, IEEE PTL, vol. 16, pp. 1017-1019 (2004)


• Standing-wave cavity

SOA

PC C/L Coupler

FBG

10:90

Output

50:50

OSA

PC

HiBiFiber

1548 1552 1556 1560 1564 1568-24

-20

-16

-12

-8

-4

Wavelength (nm)

Tra

nsm

issi

on

(d

B)

Grating Transmission

SFL with a CFPR

V. Baby et al, CIPI Project IT2

FSR = 25 GHz


1545 1550 1555 1560 1565 1570-60

-40

-20

0

1545 1550 1555 1560 1565 1570-60

-40

-20

0

Variation of Laser with 23nm HiBi Filter, using Polarization Control

1545 1550 1555 1560 1565 1570-60

-40

-20

0

1545 1550 1555 1560 1565 1570-60

-40

-20

0

1545 1550 1555 1560 1565 1570-60

-40

-20

0

1545 1550 1555 1560 1565 1570-60

-40

-20

0O

utp

ut P

ow

er

(dB

m)

Wavelength (nm)Wavelength (nm)

Ou

tpu

t Po

we

r (d

Bm

)

Wavelength (nm)

Ou

tpu

t Po

we

r (d

Bm

)

Wavelength (nm)

Ou

tpu

t Po

we

r (d

Bm

)O

utp

ut P

ow

er

(dB

m)

Wavelength (nm)

Ou

tpu

t Po

we

r (d

Bm

)

Wavelength (nm)

• Tunable operation by adjusting PC in HiBi-FLM

SFL with a CFP Resonator



1548 1552 1556 1560 1564 1568-60

-50

-40

-30

-20

-10

0

Wavelength (nm)

Ou

tpu

t Po

we

r (d

Bm

)Laser Spectrum using 23nm HiBi Filter

SFL with a CFP Resonator

9 dB


• Photonic code conversion in packet-switched networks with code-based processing (CIPI Project IT2)

Application of Multi-wavelength SFL

Code Contention System

Switch

Contention Resolution

(Label switching)

R. E. Gordon and L. R. Chen, IEEE PTL, vol. 18, pp. 586-588 (2006)


Photonic Code Conversion: Schematic and Principle

PC1

SOA1 SOA2

AWG

λj1 λj2 λj3 λj4

Output Code j

10%

90%PC2

VOA

TLS1

TLS2

TLS3

TLS4

4

x

1

MOD EDFA

Isolator

λi1λi2λi3λi4

Loop Mirrors

OCA

OCB

CONTROL ARM

RING

Input Code i

PCC

PD Rx

SAT

OFF

ON


PC1

SOA1 SOA2

AWG

λj1 λj2 λj3 λj4

Output Code j

10%

90%PC2

VOA

TLS1

TLS2

TLS3

TLS4

4

x

1

MOD EDFA

Isolator

λi1λi2λi3λi4

Loop Mirrors

OCA

OCB

CONTROL ARM

RING

Input Code i

PCC

PD Rx

UNSAT

ON

OFF

Photonic Code Conversion: Schematic and Principle


PCC Results

-70

-60

-50

-40

-30

-20

-10

1532 1534 1536 1538 1540 1542 1544

Input Code

Output Code

Wavelength (nm)

Pow

er

(dB

m)

λi

1

λi

2

λi3 λi

4

λj1 λj2 λj3 λj4 PCC setup:

ISOA,1 = 36mAISOA,2 = 139mA

-60

-55

-50

-45

-40

-35

-30

-25

-12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2

Total Input Power (dBm)

Peak O

utp

ut

Pow

er

(dB

m)

Static Response Summary:

• 4.7dB Input swing

• 23.3dB Output swing

• Sharp, step-like transition

• Thresholding and limiting functionality

• 2R regeneration possible


• Measuring chromatic dispersion based on time-of-flight

V. Pagé and L. R. Chen, Opt Commun (to appear, 2006)

Applications of Tunable Multi-wavelength SFL


• Measurements using both wavelength spacings

Measuring CD based on TOF: Results


• CD measurements for both wavelength spacings and comparison to standard phase-shift technique

Measuring CD based on TOF: Results


• Tunable photonic microwave filter

L. R. Chen and V. Pagé, IEE EL, vol. 41, pp. 1183-1184 (2005)

multi-optical source

RF out

electro-opticmodulator

dispersivemedium

SMF

fRF

lightwave componentanalyzer

EDFA

N

mRFm

RFRF DfmjP

fc

DfH

1

220 1exp

2cos

DFSR

1

Applications of Tunable Multi-wavelength SFL

0 2 4 6-50

-40

-30

-20

-10

0

no

rma

lize

d fi

lter

resp

on

se, d

B

frequency, GHz

0 2 4 6-50

-40

-30

-20

-10

0

= 3.2 nm

= 1.6 nm

• Microwave filter response (using 9.5 km of SMF as dispersive medium)


• Using SOA as a gain medium allows for:– Stable, multi-wavelength operation at room

temperature– Narrow wavelength spacings (25 GHz demonstrated)– Relatively simply implementation

• Issues for further study:– Power equalization– Single longitudinal mode operation

Summary

Multi-wavelength Semiconductor Fiber Lasers

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