Resonantly Enhanced Nonlinearity in Doped Fibers for Low-Power All-Optical Switching: A Review

The authors report measurements of ultrafast all-optical switching in dual-core fiber nonlinear couplers. By performing the measurements with square optical pulses, the pulse breakup which occurs in experiments performed by using conventional bell-shaped pulses is minimized. Compared to measurements performed by using conventional bell-shaped pulses, the measurements yield decreased switching power, a sharper switching transition, and improved power transfer. It is concluded that square pulse switching can be utilized to enhance the switching performance of any ultrafast all-optical switching device triggered by instantaneous intensity. >

Use of femtosecond square pulses to avoid pulse breakup in all-optical switching

A mathematical model of the strong, resonantly enhanced nonlinear phase shift recently reported in Er-doped fibers which relates the phase shift and signal loss to the fiber parameters and the pump and signal wavelengths, is presented. Predictions are in fair agreement with the phase shift and loss measured in an experimental Er-doped fiber switch based on this effect. A strong, nearly wavelength independent contribution to the nonlinear phase shift is observed in the switch. The model suggests that this effect is due to the same nonlinear effect arising from one or more vacuum ultraviolet (VUV) transitions in Er/sup 3+/. >

Analysis of nonlinear optical switching in an erbium-doped fiber

All-optical switching is demonstrated in a 200-m-long fiber nonlinear Mach–Zehnder interferometer. The only stabilization mechanism used is passive enclosure of the interferometer. Stable operation is obtained by using a twin-core fiber. The experiment demonstrates the feasibility of use of fiber nonlinear Mach–Zehnder interferometers for ultrafast switching and pipeline logic.

All-optical switching in a 200-m twin-core fiber nonlinear Mach–Zehnder interferometer

We describe a two-mode fiber switch made of a short length of erbium-doped fiber in which switching is accomplished by a nonlinearity that is resonantly enhanced by the dopant. In a 0.95-m fiber pumped with a 1.48-μm laser diode, a 906-nm signal is switched with only 8 mW of absorbed power at a signal absorption loss of 0.25 dB.

Laser-diode-pumped nonlinear switch in erbium-doped fiber

A new optical–optical switching technique is proposed and demonstrated with a probe–pump scheme, utilizing nonlinear differential phase shift between two spatial modes in a highly elliptical-core fiber. The probe beam is switched from one intensity-lobe position of the fiber output radiation pattern to the other in a 33-m-long fiber at a pump power of 1.6 W.

C. C. Pohalski

Papers

Optical Kerr switch using elliptical-core two-mode fiber.