Samsung Electronics Co., Ltd.

Korea Advanced Institute of Science and Technology

Teralink Communications, Inc.

Yun-Chur Chung

Jin-Hwan Jang

Hoon Bae Kim

Hoon Sik Kim

Keun-Joo Park

Seung-Kyun Shin

Jun-Haeng Lee

Kwan-Seop Lee

It is disclosed that a method and apparatus that automatically monitors each channel's optical signal-to-noise ration (OSNR) using optical filter and polarization extinction method in wavelength division multiplexing (WDM) scheme-based optical transmission systems. OSNR is simply measured using optical filter by comparing amplified spontaneous emission (ASE) over the signal band, of which bandwidth has changed, while leaving signal intensity intact, with that original signal and, OSNR measurement is allowable over a wider range of OSNR by minimizing the ratio of signal to ASE over the signal band using polarization extinction method.

OSNR monitoring method and apparatus for the optical networks

A cold-start wavelength-division-multiplexed (WDM) optical transmission system uses a synchronized etalon filter, DFB lasers and passive optical demultiplexers. The DFB lasers are tested under normal operating conditions and wavelength-selected for each channel. The wavelength selection is such that the laser operates within one half of the channel spacing from the standardized wavelength. For the cold-start operation, each laser is able to automatically find its operating wavelength without any prior knowledge of its operating conditions for the standardized wavelength. In addition, this system simultaneously adjusts the output power of each laser to a desired value. Also provided is a method for generating standardized frequencies for a wavelength-division-multiplexed optical transmission system, including the step of adjusting the incident angle of an etalon filter by employing two frequency-locked lasers to compensate for differences of the thickness and refractive index of the etalon filter, and the step of fixing the position of the etalon filter to permanently have the adjusted incident angle, the etalon filter having resonant frequencies respectively corresponding to standardized frequencies.

Cold-start wavelength-division-multiplexed optical transmission system

The present invention relates to a sliding-frequency guiding filter which is capable of guiding soliton pulses to hundreds of different resonant frequencies by designing the device so that the filter can automatically offset its peak resonant frequency from the frequency of incoming soliton pulses. The sliding-frequency guiding filter comprises the followings: a coupler to tap some of incoming soliton signals; a wafer whose one half is coated by multilayered dielectric on both sides while leaving the other half uncoated, where the soliton signals tapped through the coupler is directed to coated half and uncoated half of the wafer, respectively; and, a thermoelectric cooler attached to the coated side of the wafer. The sliding-frequency guiding filter, made of the same design, can be applied throughout the soliton transmission line instead of the numerous filters all operating at different resonant frequencies. Accordingly, the sliding-frequency guiding filter can be practically used in ultralong distance soliton transmission system.

Sliding-frequency guiding filter for soliton transmission

Growing community of inventors

Taejon, South Korea

Yun-Chur Chung