1. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen Multi-wavelength Semiconductor Fiber Lasers Lawrence R. Chen Photonic Systems Group Department of Electrical and Computer Engineering McGill University Montreal, Quebec, Canada lawrence.chen@mcgill.ca

2. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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.

3. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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

4. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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

5. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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

6. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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

7. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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

8. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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) Sampled FBG: periodic comb filter with wavelength spacing set by the sample period P

9. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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) Due to the different effective indices of the x and y polarizations in the HiBi fiber, each polarization will have its own reflection peak 

10. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen > 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 dBVOA = 8.5 dBVOA = 14 dB

11. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 75 wavelengths with 40 GHz spacing SFL with a PLC-Based Delayed Interferometer DI spectral responseLaser output increasing cavity loss H. Dong et al, IEEE PTL, vol. 17, pp. 303-305 (2005)

12. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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)

13. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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)

14. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 20 wavelengths with 100 GHz spacing using multi- wavelength thin film etalon filter SFL with a Linear Optical Amplifier Sample laser output

15. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen Comparison of power stability SFL with a Linear Optical Amplifier LOA SOA

16. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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) PC 1 HiBi, L 3 dB coupler in out Reflectivity of FLM depends on this phase difference: where Periodicity given by

17. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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

18. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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 … PC 1 HiBi, L 1 PC 2 HiBi, L 2 PC N HiBi, L N 2  2 switch 3 dB coupler combiner in out As a simple demonstration, we use two fiber segments and one switch –For the cross-state, –For the bar state, PC 1 HiBi, L PC 2 HiBi, L 2  2 switch 3 dB coupler combiner in out

19. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen Digitally Programmable HiBi-FLM Switch in cross-state L = 1.99 m    3.2 nm insertion loss  7 dB Switch in bar state L = 3.98 m    1.6 nm insertion loss  10 dB After changing the state of the switch, may need to adjust PC to optimize contrast Results

20. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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

21. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen Tunable SFL Stability: repeated scans of output spectra Output power fluctuations < 1.5 dB Wavelength variations < 0.05 nm Switch in cross-state ( = 3.2 nm)Switch in bar state ( = 1.6 nm)

22. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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 21 wavelengths with 100 GHz spacing

23. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen Increased wavelength range of operation SFL with HiBi-FLM and Hybrid SOA-EDFA Gain Medium Y.-G. Han et al, IEEE PTL, vol. 17, pp. 989-991 (2005) Tunable wavelength spacing Tunable wavelengths

24. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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)

25. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen Standing-wave cavity SFL with a CFPR V. Baby et al, CIPI Project IT2 FSR = 25 GHz

26. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen Tunable operation by adjusting PC in HiBi-FLM SFL with a CFP Resonator

27. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 35 wavelengths with 25 GHz spacing SFL with a CFP Resonator 9 dB

28. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen Photonic code conversion in packet-switched networks with code-based processing (CIPI Project IT2) Application of Multi-wavelength SFL R. E. Gordon and L. R. Chen, IEEE PTL, vol. 18, pp. 586-588 (2006)

29. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen Photonic Code Conversion: Schematic and Principle PC 1 SOA 1 SOA 2 AWG λ j1 λ j2 λ j3 λ j4 Output Code j 10% 90% PC 2 VOA TLS 1 TLS 2 TLS 3 TLS 4 4x14x1 MOD EDFA Isolator λi1λi1 λ i2 λ i3 λ i4 Loop Mirrors OC A OC B CONTROL ARM RING Input Code i PCC PD Rx SAT OFF ON

30. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen PC 1 SOA 1 SOA 2 AWG λ j1 λ j2 λ j3 λ j4 Output Code j 10% 90% PC 2 VOA TLS 1 TLS 2 TLS 3 TLS 4 4x14x1 MOD EDFA Isolator λi1λi1 λ i2 λ i3 λ i4 Loop Mirrors OC A OC B CONTROL ARM RING Input Code i PCC PD Rx UNSAT ON OFF Photonic Code Conversion: Schematic and Principle

31. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen PCC Results Wavelength (nm) Power (dBm) λ i1 λ i2 λ i3 λ i4 λ j1 λ j2 λ j3 λ j4 PCC setup: I SOA,1 = 36mA I SOA,2 = 139mA Total Input Power (dBm) Peak Output Power (dBm) Static Response Summary: 4.7dB Input swing 23.3dB Output swing Sharp, step-like transition Thresholding and limiting functionality 2R regeneration possible

32. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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

33. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen Measurements using both wavelength spacings Measuring CD based on TOF: Results

34. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen CD measurements for both wavelength spacings and comparison to standard phase-shift technique Measuring CD based on TOF: Results

35. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen Tunable photonic microwave filter L. R. Chen and V. Pagé, IEE EL, vol. 41, pp. 1183-1184 (2005) multi- optical source RF out electro-optic modulator dispersive medium SMF f RF lightwave component analyzer EDFA Applications of Tunable Multi-wavelength SFL  = 3.2 nm  = 1.6 nm Microwave filter response (using 9.5 km of SMF as dispersive medium)

36. 5/19/2006CIPI Workshop on Fiber Lasers L R Chen 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