| 简介 |
An apparatus for gating an optical signal comprising : an input stage (70, 72, 74, 62, 64) arranged to receive and combine first and second optical control signals (ON, OFF) of first and second wavelengths, and an optical signal (SIGNAL IN) to be gated of a third wavelength. A gain medium (66) is arranged to receive the signals SIGNAL IN, ON and OFF from the input stage. The gain medium (e.g. YAG) comprises a transition metal dopant (e.g. Cr4+) that has an excited state populatable by the first control signal and depopulatable by the second control signal to allow selective amplification of the optical signal to be gated by stimulated emission from the excited state responsive to the control signals. The amplification process has a very fast switch-on time that is several orders of magnitude faster than in prior art devices based on the rare earth dopant Er3+. This allows the apparatus to be used for high-speed optical switching applications, such as routing of data packets in an optical packet switching network. After transmission of the optical signals through the gain medium, an output stage comprising a wavelength selective filter (68) is used to reject the control signals (ON, OFF) but transmit the optical signal for output (SIGNAL OUT) from the apparatus. |
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