We previously studied the same SRS propagation equations using stochastic initial conditions and partially coherent pulses
The experimentally reported sensing distance in this contribution is only 8 m owing to the pulse repetition rate of the mode-locked laser used to generate the narrow coherent pulses. The technique requires a high bandwidth at the receiver, with components used in the demodulation being a 35 GHz photodiode and a digitizer with a sampling rate of 80 GS/s.
When light from a coherent pulse reaches each element, it will be backscattered, and since the field contributions from adjacent elements within the spatial length of the pulse have similar phase relations owing to the coherence of the light, the backscattering field from each one will interfere at the receiver.
The electric field at the receiver (z = 0) which is backscattered from the coherent pulse propagating along the fiber is the sum of the contributions of the fields from M random scattering elements within z [member of] [([tv.sub.g] - [w.sub.p])/2, [tv.sub.g]/2], vg being the group velocity of light and [w.sub.p] is the spatial length corresponding to the pulse duration, and is given by [6, 7]:
spectral widths of the coherent pulses
[[DELTA].sub.1] [not equal to] 0, [[DELTA].sub.2] [not equal to] 0, and [[DELTA].sub.3] [not equal to] 0, these other two lines will appear even though the phase relaxation is not taken into account (see Chapter 6).
This protocol has a higher IS level than the BB84 protocol, when weak coherent pulses but not a single photon source are used by sender (Huttner et al.
In practice for realisation of BB84 and six-state protocols weak coherent pulses with average photon number about 0.1 are used.
Initial flow visualization experiments suggested that it was difficult to produce coherent pulses using on-or-off times of less than 1 s.
Initial visualizations suggested that coherent pulses generated at the nozzle orifice were disrupted as they moved downstream but maintained cohesion for at least 100 cm, setting an approximate (and probably conservative) boundary for pulse coherence.
The SAR transmits coherent pulses
and creates the effect of a phased array by collecting the returns from each pulse as the platform moves forward.
are formed by interrupting a continuously running oscillator, so each received RF pulse will be in phase with an oscillator that is phase locked to the RF waveform of all previous pulses.