Electronics and Telecommunications Research Institute

Seo-Yeon Park

Kyong-Hon Kim

Hak-Kyu Lee

El-Hang Lee

Min-Yong Jeon

A hybrid type passively and actively mode-locked laser scheme is disclosed, in which not only the capability of producing ultra-short optical pulses by the conventional passively mode-locked optical fiber laser scheme is utilized, but also the repetition rate variation capability and the optical pulse synchronization capability of the conventional actively mode-locked laser scheme are utilized. Consequently, all the advantages of the two conventional laser schemes are obtained in the present invention. Specifically, two loops are coupled together, and one of the two loops consists of a non-linear amplifying loop of the existing passively mode-locked scheme, while the other loop includes an optical modulator and an optical gain medium for the loop to perform the function of an actively mode-locked scheme. Further the other loop includes a time delay line so as to adjust the laser oscillation repetition rate. The ultra-short optical pulses of the present invention will be applied to high speed time division multiplexed optical communication system, high speed optical signal processors, and ultrafast optical phenomenon studies.

Hybrid type passively and actively mode-locked laser scheme

A measurement of nonlinear refractive index coefficient of an optical fiber with a Sagnac interferometer, comprises the steps of employing the optical fiber in a Sagnac interferometer, splitting a signal beam into two signals, launching the two split signals into the interferometer in opposite directions, combining and detecting the signals counter-propagated in the interferometer, and detecting the refractive index coefficient of the optical fiber in accordance with the difference between the two signal powers determined by a control beam. The quasi-static phase shift of the signal beam counter-propagating the same paths of the interferometer is induced by rotating the optical fiber loop of the interferometer. The present invention gives rise to little error because it does not require precise information about the pulse width of a used beam or a high-power light.

Measurement of nonlinear refractive index coefficient of optical fiber

An all-optical signal processing apparatus of a non-linear fiber loop mirror type comprises a very high-speed all-optical switch that can be used as a reverse multiplexed switch in a high-speed time division optical communication. The apparatus includes a non-linear loop mirror for switching signal light by adjusting light using the non-linear effect of an optical fiber and the characteristics of a sagnac interferometer as the fundamental configuration. The all-optical switch is constructed so that another adjustment light having an appropriate time delay with respect to an existing adjusting light is additionally introduced in order to compensate for the limitation on the switching bandwidth imposed by the walk-off between adjusting and signal lights in a conventional non-linear optical fiber loop mirror. This compensates for the cross-talk of the noise signals due to DC components generated in the conventional apparatus. A switching window of a desirable size is obtained by properly adjusting the time delay between two adjusting lights and resolving the bandwidth limitation of the switch due to the walk-off of the adjusting and signal lights according to the timing jitter of signal light.

All-optical signal processing apparatus of non-linear fiber loop mirror

A wavelength-varying multi-wavelength optical filter laser using a single pump light source is disclosed. The laser comprises a wavelength-division multiplexing coupler for applying an output from a single pump light source, a first multi-branch optical fiber coupler for branching the light from the single pump light source into a plurality of optical paths, an erbium-doped fiber located at each of optical paths, wavelength-varying optical filters located at rear of each erbium-doped fiber in each optical paths, said wavelength-varying optical filters for generating laser outputs of different wavelengths in each optical paths, optical isolators located between the erbium-doped fiber and the wavelength-varying optical filter in each optical paths, said optical isolators for reducing interference between laser outputs to be stable, optic attenuators located at rear of the wavelength-varying optical filter in each optical paths, said attenuators for regulating a mode beating between laser outputs of different wavelengths, thereby causing the multi-wavelength laser oscillation to be possible, a second multi-branch optical fiber coupler for coupling branched-optical paths, and a variable optical fiber coupler located at rear of the second multi-branch optical fiber, said variable optical fiber coupler for regulates a coupling ratio of the second variable optical fiber coupler, thereby making the output thereof to be maximum.

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Daejeon, South Korea

Seo-Yeon Park