Patent ID: 9184561
Filing Date: 2015-11-10
Classification: H01S

Abstract:
1. A method to control an optical transmitter that provides a wavelength tunable laser diode (tunable LD), a controller, and a memory look-up-table (LUT), the tunable LD integrally having a sampled grating distributed feedback (SG-DFB) region and a chirped sampled grating distributed Bragg reflector (CSG-DBR) region including at least three segments each having a diffraction grating and a space neighbor to the diffraction grating, each of segments having a heater and an optical length satisfying a relation of: where L 1 to L 3 are respective optical lengths and K is a constant of 0.3<=K<=0.7, the method comprising steps of: evaluating parameters to define an emission wavelength of the tunable LD, the parameters including currents supplied to respective heaters, optimum offset power supplied to the heater in the first segment, and an operating temperature of the tunable LD; storing the parameters to the memory LUT; and practically operating the tunable LD by performing steps of, wherein the step of evaluating the parameters includes steps of, varying power, P where Rth 1 to Rth 3 are thermal resistance of respective heaters and offset is offset power supplied to the heater in the first segment; measuring an emission wavelength and a side mode suppression ratio (SMSR) at the emission wavelength for the offset power; evaluating a wavelength tunable range of the tunable LD, where the wavelength tunable range is a range the SMSR exceeds a preset value; iterating the steps of varying power, measuring the emission wavelength and the SMSR, and the evaluating the wavelength tunable range as varying the offset; determining the optimum offset power at which the wavelength tunable range becomes a maximum.