Patent ID: 7693366

Claim:
A device comprising: a first band-pass filter operable to receive a first optical signal from a laser and to transmit a first portion of the first optical signal; and a second band-pass filter operable to receive the first portion of the first optical signal and to transmit a second portion of the first optical signal, wherein said first band-pass filter has a first corner-pass wavelength of λ a , a first corner-stop wavelength of λ b , and a first pass-band center wavelength λ pb1 such that λ a ≦λ pbl ≦λ b , wherein said second band-pass filter has a second corner-pass wavelength of λ c , a second corner-stop wavelength of λ d , and a second pass-band center wavelength λ pb2 such that λ c ≦λ pb2 ≦λ d , and wherein λ a <λ c <λ b <λ d , wherein  ⅆ A ⅆ λ ⁢ ❘ dB ⁢ / ⁢ nm  is the magnitude of each of the filter pass-band slopes of said first and second band-pass filters, wherein λ 0 is a central wavelength of said laser, wherein CSO nat dB — elec is a native second order distortion value of said laser measured in dBc-electrical units, wherein CSO tot — deg dB — elec is a minimum allowable second order distortion value of a signal after having passed through said first and second band-pass filters, wherein N CSO is a number of second order distortion beats that comprise a distortion power at a second order distortion frequency under consideration, wherein c is the speed of light in a vacuum, wherein m is an optical modulation index 0<m≦1, wherein α is a laser chirp of said laser, wherein y is a laser slope efficiency y of said laser, wherein I is a bias current of said laser, wherein I th is a threshold current of said laser, wherein P O is an optical output power of said laser, and wherein the magnitude of each filter pass-band slope of each said first and second band-pass filters satisfies at least one of  ⅆ A ⅆ λ ⁢ ❘ dB ⁢ / ⁢ nm  ≤ 10 ln ⁡ ( 10 ) ⁢ 1 N CSO ⁢ c m ⁢ ⁢ α ⁡ ( I - I th ) ⁢ 1 λ 0 2 [ 10 - [ CSO tot_deg dB_elec 20 ] - 10 - [ CSO nat dB_elec 20 ] ] ⁢ and  ⅆ A ⅆ λ ⁢ ❘ dB ⁢ / ⁢ nm  ≤ 10 ln ⁡ ( 10 ) ⁢ 1 N CSO ⁢ c ⁢ ⁢ γ m ⁢ ⁢ α ⁢ ⁢ P O ⁢ 1 λ 0 2 [ 10 - [ CSO tot_deg dB_elec 20 ] - 10 - [ CSO nat dB_elec 20 ] ] .