Lasers in Optical Communications Rogério Nogueira

Internet traffic growing with 60 % each year Worldwide > 1500 million Internet users Estimated trans-Atlantic traffic in 2025: 400 Tbit/s Internet ~2 % global CO 2 emission What do we want from internet ? Fiber optical communication is the solution for the bandwidth demand and to reduce power consumption. Lasers play a major role in these systems. What are the requirements?

What do we need in a laser for fiber optical communications ?  High modulation bandwidth (>1 Gbit/s)  Small size  Intense single spatial mode  Energy efficient  Narrow spectral linewidth  Single longitudinal mode (monochromatic)  Reliable operation  Possibility of integration So… what are the options ?

Semiconductor laser Semiconductor laser is a laser in which semiconductor serves as photon source. Semiconductors (typically direct band-gap semiconductors) can be used as small, highly efficient photon sources.

Semiconductor laser  High modulation bandwidth (> 10 Gbit/s)  Small size -Packaged: ~ 2×1×1 cm -Unpackaged: ~ grain of salt, 0.5mm × 200  m × 100  m  Intense single spatial mode  Energy efficient  Narrow spectral linewidth  Can be single longitudinal mode (monochromatic)  Reliable operation  Can be integrated

GALACTICO - blendinG diverse photonics And eLectronics on silicon for integrAted and fully funCTIonal COherent

GALACTICO

State of the Art - Product Source: Infinera Is there any room for innovation ? (in a small laboratory)

Fiber lasers… PC EDFA / SOA FBG Circulator

Fiber Bragg Gratings Written in Hi-Bi fiber (HiBi FBG) Bow-Tie Panda IEC x y

XY Self-Generated Orthogonal Pumps PC EDFA / SOA Two Tunable HiBi FBGS Circulator

Self-Generated Orthogonal Pumps

Another version…  Simplified solution -Can be used as wavelength converter Input PC1 PC2 Circulator RSOA Hi Bi FBG Output

Wavelength Converters Input Output PC1 PC2 PC3 Circulator SOA HiBi FBG

Wavelength Converters (All-Fiber Configuration) PC1 EDFA Mach Zhender PRBS Gbit/s PC2 PC3 Circulator DSF HiBi FBG Circulator FBG Output PIN Scope Circulator Effic.: -2.5 dB SNR: 25 dB  =15 nm

Summary The development of new semicondutor lasers for optical communication systems is crucial for the current demand of more and more bandwidth. Most of the research and product development is made in a few companies and research laboratories. There are still specific applications that require other laser types, such as fibre lasers.

Thank you Rogério Nogueira

Basic Laser Structure Fabry-Perot Laser Light Cleaved facet (partial mirror) Active Region Heat Sink Laser  Wires (connection to current source) 

Semiconductor diode laser  Electrical pumping  Wide variety of wavelengths

 Lasers have some KHz of linewidth.  Wavelength is well defined.  the thermal stability is high  Monolithic integration of modulator is admissible. DFB Lasers