Difference between revisions of "Microwave Photonics"
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Direct Modulation: Shot noise : -168 dBm , Thermal noise : -174 dBm. | Direct Modulation: Shot noise : -168 dBm , Thermal noise : -174 dBm. | ||
Laser relative intensity noise(RIN): We do not desire RIN peaks in the passband. | 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. suppresion of one side band over the other(suppresion ratio) | ||
| + | Beyond a certain input power we get briulloin back scattering which saturates the output power. | ||
| + | resons for cross-talk : 1) Raman scattering 2) cross phase modulation 3) kerr effect. | ||
| + | Effects of non-linear dependence on voltage of Quantum efficiency leads to clipping of signal in either the positive or the negative cycle depending on the sign of its derivative with voltage. | ||
| + | Photodetector non-linearities: optical phase shifting is independent for the two side bands, whereas for microwave phase shifting we have to do it differentially. | ||
| + | Mixers : (+/-)(f1 (+/-) f2) | ||
| + | Beam forming: Power added efficiency(PAE) = P(rf)/(P(out)+(V_bias*I_bias));(typically 30-40%) | ||
| + | problem with photonic sampling ADC is how do we quantize the signal(optical wave packet). | ||
| + | Phase noise in photodetectors. | ||
Latest revision as of 12:25, 29 March 2010
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. suppresion of one side band over the other(suppresion ratio) Beyond a certain input power we get briulloin back scattering which saturates the output power. resons for cross-talk : 1) Raman scattering 2) cross phase modulation 3) kerr effect. Effects of non-linear dependence on voltage of Quantum efficiency leads to clipping of signal in either the positive or the negative cycle depending on the sign of its derivative with voltage. Photodetector non-linearities: optical phase shifting is independent for the two side bands, whereas for microwave phase shifting we have to do it differentially. Mixers : (+/-)(f1 (+/-) f2) Beam forming: Power added efficiency(PAE) = P(rf)/(P(out)+(V_bias*I_bias));(typically 30-40%) problem with photonic sampling ADC is how do we quantize the signal(optical wave packet). Phase noise in photodetectors.
