Microwaves Photonic Links: Components and Circuits

Chapter 6

Complement to Microwave Photonic Link Performances

6.1. Microwave signal attenuation during double sideband modulation

6.1.1. Double sideband modulation recall

In a microwave photonic link, if the amplitude modulation occurs in the laser (direct modulation) or in a Mach-Zehnder or electro-absorption modulator (external modulation) biased at V_π/2, as long as the modulation index is low, this modulation results in two sidebands around the optical carrier. If the optical angular frequency is ω_opt and the RF angular frequency is ω_RF, the electric field of the modulated wave is expressed:

[6.1] 

The Fourier transform of such a signal is constituted of three Dirac lines in the frequency space. E is obtained from its complex notation E₁ by expression:

[6.2] 

After having developed the functions of [6.1] in exponential sums, expression of E₁ is given by expression:

[6.3] 

Figure 6.1. Optical carrier amplitude modulated by a RF

6.1.2. Recall of single-mode optical fiber propagation characteristics

Figure 6.2 illustrates the cross-section of a single-mode fiber where the fiber core ...