Intensity modulation of optical signals

A method of intensity modulating an optical data signal, the method comprising:

• (a) impressing in a fast freguency response first element an intensity modulation that is non-inverting, as well as a phase modulation, on a first optical signal responsive to an intensity modulation camed by a second optical signal, using cross phase modulation;
• (b) impressing in a second element a further intensity modulation that is non-inverting on the first optical signal, after the cross phase modulation, responsive to said phase modulation;
• and
• (c) combining the intensity modulation of the first element and the further intensity modulation of the second element to improve the overall transfer function of the first and second element.

A device for intensity modulating an optical data signal, the device comprising:

• a first stage arranged to impress an intensity modulation that is non-inverting as well as a phase modulation on a first optical signal of a first frequency (ω1/2π) responsive to an intensity modulation carried by a second optical signal of a second frequency using cross phase modulation in a non-linear optical element, the phase modulation being associated to a maximum instantaneous frequency deviation (Δfmax);
• and
• a second stage arranged to impress a further intensity modulation that is non-inverting on the first optical signal, after the cross phase modulation, responsive to the phase modulation impressed on the first optical signal in the first stage,
• wherein:
• the second stage has a transfer function of transmission versus frequency that is non-linear and has a low transmission value (Tlow) at the first frequency (ω1/2π) and a high transmission value (Thigh) at a frequency equal to the first frequency plus the maximum instantaneous frequency deviation (ω1/2π+Δfmax);
• the transfer function of the second stage has a frequency width Δν defined between a minimum transmission value at the first frequency (ω1/2π) and a maximum transmission value (Tmax) at frequencies greater than the first frequency plus the frequency width (ω1/2π+Δν);
• and
• the first and second stages are matched so that the high transmission value is equal to at least half the maximum transmission value (Thigh≧0.5Tmax).

A method of intensity modulating an optical data signal, the method comprising:

• (a) impressing an intensity modulation that is non-inverting, as well as a phase modulation, on a first optical signal at a first frequency (ω1/2π), responsive to an intensity modulation carried by a second optical signal at a second frequency, using cross phase modulation, the phase modulation being associated to a maximum instantaneous frequency deviation (Δfmax);
• and
• (b) impressing a further intensity modulation that is non-inverting on the first optical signal, after the cross phase modulation, responsive to said phase modulation,
• wherein:
• the further intensity modulation is impressed using a transfer function of transmission versus frequency that is non-linear and has a low transmission value (Tlow) at the first frequency (ω1/2π) and a high transmission value (Thigh) at a frequency equal to the first frequency plus the maximum instantaneous frequency deviation (Δfmax);
• the transfer function has a frequency width Δν defined between a minimum transmission value at the first frequency (ω1/2π) and a maximum transmission value (Tmax) at frequencies greater than the first frequency plus the frequency width (ω1/2π+Δν);
• and
• the high transmission value is equal to at least half the maximum transmission value (Thigh≧0.5Tmax).