Microwave Photonics

Basic components: RF -> optical : CW source and a modulator. opical -> RF : Photodetector. OIP3 (output intercept point). Assumption in all math: output noise independent of input power. phase change with thermal conductivity: optical fibre is chosen over RF cable. Direct Modulation: Shot noise : -168 dBm , Thermal noise : -174 dBm. Laser relative intensity noise(RIN): We do not desire RIN peaks in the passband. shot noise = 2*q*I*R*B. B- Bandwidth, linear with current. thermal noise = k*T*B. We would like to approach the shot noise limited performance. RIN is proportional to (I^2). Noise factor = (effective input noise)/(Thermal noise). Effective input noise is (output noise)/(Gain). OIP3 = 4*R*(I^2)*(sin(^2)(delta phi)). 4*R*(I^2) at quadrature point. Noise figure in cascaded systems. SFDR - spur free dynamic range. CDR - compression dynamic range. some relationships if photocurrent increases gain increses, noise factor decreases, SFDR increases. if V(pi) decreases gain increases, Noise factor decreases, SFDR decreases(maybe). MZM transfer function is a sinusoid. Single side band modulation.<math>&pi</math>