Finnegan, Henderson, Farabow, Garrett & Dunner, L.L.P.
Method and device for measuring a noise figure in optical amplifiers
 A method and device for automatically and accurately measuring a noise figure of an optical amplifier are disclosed. In the method, light pulses which have different wavelengths .lambda..sub.1 .about..lambda..sub.n and have a period shorter than a time constant of extinction of the optical amplifier are generated. The light pulses thus generate are supplied to the optical amplifier. Powers P.sub.AMP1 .about.P.sub.AMPn of amplified lights outputted from the optical amplifier which correspond to the light pulses and have the wavelength .lambda..sub.1 .about..lambda..sub.n and powers P.sub.ASE1 .about.P.sub.ASEn of lights which have the wavelength .lambda..sub.1 .about..lambda..sub.n and are outputted from the optical amplifier when the amplified lights are not outputted from the optical amplifier are measured. Noise figures NF.sub.1 .about.NF.sub.n at the wavelengths .lambda..sub.1 .about..lambda..sub.n the optical amplifier are calculated according to the following equation. EQU NF.sub.k =(P.sub.ASEk /h.nu..sub.k G.sub.k Bo)+(1/G.sub.k) (k=1.about.n) In the above equation, h is Planck's constant; .nu..sub.k (k=1.about.n) are light frequencies of the light pulses; G.sub.k (k=1.about.n) are gains at the wavelengths .lambda..sub.k (k=1.about.n) of the optical amplifier; and Bo is a band width of a pass band of an instrument which is used for measuring the power P.sub.ASE1 .about.P.sub.ASEn. 
Nippon Telegraph And Telephone Corporation Ando Electric Co., Ltd.
H H
H04B H04B
inventional inventional
Tohru Kazuo
Mori Aida