Page 229 - Introduction to Information Optics

214 4. Switching with Optics

PULSES

Input energy

2
2
Fig. 4.11. The transmission |£ 20| /|£ in| of a NOLM as a function in input energy for a
continuous-wave signal, nonsoliton pulse signal, and soliton signal. [10].
After they travel around the loop of the length L. the fields E 30 and £ 40 are
given by

£ =
(4.22)
2
£40 =J^- <?£inexp[j(l - q)\E in 27in 2L//].
Using a similar relationship for the output coupling, we obtain

2
2
E 20\ = 2q(\ - q)(\ + cos[(l - 2q)\E, n 2nn 2L/Z])}. (4.23)
The extremes of the output occur when q is not equal to ?, and

2
(1 - 2q)\E in\ 2n 2L/A = m. (4.24)
We can find the required switching energy from this equation. When m is odd,
all the power emerges from port 2. When m is even, £ 20 has a minimum
transmitted power, which is equal to the linear output power (n 2 = 0), given by

(4.25)

This amount determines the switching contrast ratio. The transmission func-
2
2
tions \E 20\ /\E in\ for both a continuous-wave signal and a soliton signal are
shown in Fig. 4.11 [10].