# . *<sup>B</sup> B C P P P*

At last, K4 coupling factor calculation follows the setup depicted in **Figure 6**. When the input optical power is injected on Port #D, then we should bias SOA2, and SOA1 should remain unbiased. If the selected input is port #A, then SOA1 should be biased and SOA2 switched off.

3

If the input is either port #B or #C, then anyone of the two SOAs can be used.

#A

PC

**Figure 6.** Setup for the characterization of K4 coupling factor.

**Table 1.** Procedure for measurements and calculations.

#B

#D

K3

Power measurement is taken at ports #I and #J. Coupling factor 4 is given by,

4

a

( ) #
