Chapter for InTech e-book on : injection locked FP LD for Access Networks (http://www.intechweb.org/)

The design of two-section Fabry-Perot (FP) laser diodes for polarisation insensitive injection locking is detailed and its functionality demonstrated with an experiment showing error free transmission through 50km over 20nm at 2.5Gb/s. 10Gb/s operation is also demonstrated with a quantum dots-based FP laser diode. matched to that of incoming signal. For an input signal with TE polarization, one TE mode with a wavelength very close to that of the input signal can be locked to the incoming signal. But once the polarisation of the incoming signal changes to TM, injection locking will disappear as the detuning between the input wavelength and the closest TM mode is larger than the locking range. To tackle this, a two section FP LD is designed by using a PIS-gain material as the active section, and a strained InGaAsP material as the birefringence compensating section. As a result, the optical emission spectrum shows superimposed TE and TM modes after the proper amount of electrical currents are injected into both sections. In this case, TE and/or TM mode will be locked to the incoming signal whatever its polarisation state. This paragraph will show schemes and figures to detail the design of two-section FP LDs for polarization insensitive injection locking. III. Chip fabrication Bulk material based on classical PIS gain SOA with gain peak around 1550 nm is first grown on InP wafer. After the removal of the active gain layers on parts of the wafer, a regrowth of the strained InGaAsP layer with a peak luminescence at 1545nm is done to form butt joints with the active gain layers.