hi all
The RSOAs have a high reflectivity coating on one facet and an ultra low reflectivity coating (<10-5) on the other. The input facet is angled and to achieve a normal and a 10 degree angled facet on the same device the gain region is curved close to the centre of the chip with a bend with radius of 3mm. To further reduce the effective facet reflectivity and improve coupling, the device output far field is reduced through the linear tapering of the active region is in the lateral direction from 1.2µm to approximately 0.45µm over 80µm approaching the angled facet. The key parameters of interest for an optical amplifier are gain, Noise Figure (NF), polarization dependent gain (PDG) and maximum saturable output power (Psat); with RSOAs, modulation bandwidth is also relevant. A parametric performance summary of the key operational parameters of a pigtailed TO style packaged RSOA device at a drive current of 80mA is shown in Figure 1 and Figure 2. S-band devices (Figure 1) exhibit excellentgain (over 20dB from 1470 nm upwards), with Psat rising to a maximum of 7.5dB at 1530nm. The NF peaks at
10.5dB at 1465nm but is generally <10dB. Small signal PDG is less than 2.8dB across the band and ripple is less than 2.2dB; both will reduce substantially in operation as the gain is compressed. For C/L-band devices at a drive current of 50mA, more than 20dB of gain can be observed from 1535nm upwards, with Psat rising to a maximum of 6dB at 1580nm.
Regards