Review questions for HW 3

1. What optical phenomenon is grating based? What operations it can perform in WDM optical network?

It is based on interference. It can be used for multiplexing and demultiplexing.

2. For a forward propagating wave, what is the polarity of its phase inside the propagation factor?

negatvie

3. For a retarder, its refractive index along x axis is smaller than that of the y axis. which axis is the faster axis?

x is fast axis since its n is smaller.

4. The e field of an EM wave equals to hat x E_1 cos ( omega t - kz + phi_x ) + hat y E_2 cos ( omega t - kz + phi_y ) . Write the phasor form E.

hat x E_1 exp (-j kz + j phi_x ) + hat y E_2 exp ( -j kz + j phi_y )

5. What are the conditions for right circular polarization for the wave in question 4.?

phi_y - phi_x = - pi / 2

6. What material can be used to fabricate retarder (also called wave plate)?

Anisotropic media e.g. birefringent materials with x and y basis

7. What material can be used to make rotator?

Anisotropic material with right circular and left circular basis .

8. What is the major difference between retarder and rotator?

They operate with different bases.

9. What material can be used to make a frequency mixer?

Nonlinear media.

10. What material can be used to make a grade index lens?

Inhomogeneous material.

11. Why nonlinear effects are bad for signal transmission?

It takes energy out of the intented communication channel and introduce interference to another channel (cross talk).

12. Why dispersion is bad for transmission? What device can compensate for it?

It casuses widening of pulses. Prism or grating can cancel dispersioin.