Fiber Optic Wiki

Impulse response of the photonic time-stretch (PTS) system

September 28, 2011

Fig. 3 Capture of a 95-GHz RF tone using the photonic time-stretch digitizer. The signal is captured at an effective sample rate of 10-Terasamples-per-second.

The time-lens concept : Comparison with time lens imaging

September 28, 2011

Another technique, that involves a time lens, can also be used to slow down (mostly optical) signals in time. The time-lens concept relies on the mathematical equivalence between spatial diffraction and temporal dispersion, the so called space-time duality. A lens held at fixed distance from an object produces a magnified image visible to the eye. The lens imparts a quadratic phase shift to the spatial frequency components of the optical waves; in conjunction with the free space propagation (object to lens, lens to eye), this generates a magnified image. Owing to the mathematical equivalence between paraxial diffraction and temporal dispersion, an optical waveform can be temporally imaged by a three-step process of dispersing it in time, subjecting it to a phase shift that is quadratic in time (the time lens itself), and dispersing it again. Theoretically, a focused aberration-free image is obtained under a specific condition when the two dispersive elements and the phase shift satisfy the temporal equivalent of the classic lens equation. Alternatively, the time lens can be used without the second dispersive element to transfer the waveform’s temporal profile to the spectral domain, analogous to the property that an ordinary lens produces the spatial Fourier transform of an object at its focal points.

Relative intensity noise(RIN)

September 28, 2011

Relative intensity noise (RIN), describes the instability in the power level of a laser. The noise term is important to describe lasers used in fiber-optic communication and LIDAR remote sensing.

Optical Internetworking Forum

September 28, 2011

The Optical Internetworking Forum (OIF) was organized to facilitate and accelerate the development of next-generation optical internetworking products. The OIF produces Electrical, Tunable Laser, Very Short Reach Hardware Interfaces.

How Time-stretch analog-to-digital converter works?

September 27, 2011

A time-stretch analog-to-digital converter (with a stretch factor of 4) is shown. The original analog signal is time-stretched and segmented with the help of a time-stretch preprocessor (generally on optical frontend). Slowed down segments are captured by conventional electronic ADCs. The digitized samples are rearranged to obtain the digital representation of the original signal.

Impulse response of the photonic time-stretch (PTS) system

September 27, 2011

Capture of a 95-GHz RF tone using the photonic time-stretch digitizer. The signal is captured at an effective sample rate of 10-Terasamples-per-second.

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