Power source for a dispersion compensation fiber optic system

Abstract

This invention generally relates to an optical filter for a fiber optic communication system. An optical filter may be used, following a directly modulated laser source, and converts a partially frequency modulated signal into a substantially amplitude modulated signal. The optical filter may compensate for the dispersion in the fiber optic transmission medium and may also lock the wavelength of the laser source.

1 . A fiber optic communication system, comprising: 
 an optical signal source adapted to produce a partially frequency modulated signal; and    an optical discriminator adapted to convert the partially frequency modulated signal into a substantially amplitude modulated signal, where the optical discriminator is adapted to compensate for at least a portion of a dispersion in a transmission fiber.    
   
   
       2 - 35 . (canceled)  
   
   
       36 . A fiber optic communication system, comprising: 
 an optical signal source adapated to produce a partially frequency modulated signal;    an optical discriminator having an associated dispersion D d  with a either a positive or negative sign adapted to convert the partially frequency modulated signal to a substantially amplitude modulated signal; and    a transmission medium having an associated dispersion D f  with either a positive or negative sign, where the sign of D d  is an opposite sign of D f .    
   
   
       37 . The fiber optic communication system according to  claim 36 , where the optical signal source is a directly modulated laser.  
   
   
       38 . A fiber optic communication system according to  claim 37 , where the directly modulated laser is adapted to produce signals with a 2-7 dB extinction ratio.  
   
   
       39 . The fiber optic communication system according to  claim 36 , where the optical discriminator is at least a portion of a band pass filter.  
   
   
       40 . The fiber optic communication system according to  claim 39 , where the band pass filter operates in reflection.  
   
   
       41 . The fiber optic communication system according to  claim 39 , where the portion of the band pass filter is a high pass filter.  
   
   
       42 . The fiber optic communication system according to  claim 39 , where the portion of the band pass filter is a low pass filter.  
   
   
       43 . The fiber optic communication system according to  claim 36 , where the optical discriminator is a thin film filter.  
   
   
       44 . The fiber optic communication system according to  claim 43 , where the optical discriminator is formed by a transmission edge of the thin film filter.  
   
   
       45 . The fiber optic communication system according to  claim 36 , where the optical discriminator has a positive slope.  
   
   
       46 . The fiber optic communication system according to  claim 36 , where the substantially amplitude modulated signal has an output extinction ratio greater than about 10 dB.  
   
   
       47 . The fiber optic communication system according to  claim 36 , where the optical discriminator has a negative slope.  
   
   
       48 . The fiber optic communication system according to  claim 36 , where the optical discriminator is formed by cascading a number of non-interfering multicavity thin film filters.  
   
   
       49 . The fiber optic communication system according to  claim 36 , where the optical discriminator is a coupled multi-cavity filter.  
   
   
       50 . The fiber optic communication system according to  claim 36 , where the optical discriminator operates in reflection.  
   
   
       51 . The fiber optic communication system according to  claim 36 , where the optical discriminator operates in transmission.  
   
   
       52 . The fiber optic communication system according to  claim 36 , where the optical discriminator is a fiber Bragg grating filter.  
   
   
       53 . The fiber optic communication system according to  claim 52 , where the Bragg grating filter is formed in a fiber.  
   
   
       54 . The fiber optic communication system according to  claim 52 , where the Bragg grating filter is formed in a planar waveguide.  
   
   
       55 . The fiber optic communication system according to  claim 36 , where the optical discriminator is a periodic filter.  
   
   
       56 . The fiber optic communication system according to  claim 36 , where the optical discriminator is a multi-cavity etalon where the dispersion D d  of the optical discriminator occurs at a multiplicity of equally spaced wavelengths.  
   
   
       57 . The fiber optic communication system according to  claim 55 , where the optical discriminator is a sampled Bragg grating filter.  
   
   
       58 . The fiber optic communication system according to  claim 57 , where the sampled Bragg grating filter is formed in a fiber.  
   
   
       59 . The fiber optic communication system according to  claim 57 , where the sampled Bragg grating filter is formed in a planar waveguide.  
   
   
       60 . The fiber optic communication system according to  claim 55 , where the optical discriminator is a waveguide grating router.  
   
   
       61 . The fiber optic communication system according to  claim 55 , where the optical discriminator is a series of cascaded etalon filters.  
   
   
       62 . The fiber optic communication system according to  claim 36 , where the optical signal source is a single wavelength semiconductor laser.  
   
   
       63 . The fiber optic communication system according to  claim 36 , where the optical signal source is a vertical cavity surface emitting laser.  
   
   
       64 . The fiber optic communication system according to  claim 36 , where the optical signal source is an externally modulated laser.  
   
   
       65 . The fiber optic communication system according to  claim 64 , where the optical signal includes a continuous wave laser and a phase modulator.  
   
   
       66 . The fiber optic communication system according to  claim 36 , where the phase modulator is a semiconductor modulator.  
   
   
       67 . The fiber optic communication system according to  claim 36 , where the phase modulator is a LiNbO 3  phase modulator.  
   
   
       68 . The fiber optic communication system according to  claim 36 , where the phase modulator is a semiconductor optical amplifier.  
   
   
       69 . The fiber optic communication system according to  claim 36 , where the optical signal source is a tunable semiconductor laser.  
   
   
       70 . The fiber optic communication system according to  claim 69 , where the tunable semiconductor laser is a distributed Bragg reflector laser.  
   
   
       71 . The fiber optic communication system according to  claim 69 , where the tunable semiconductor laser is a sampled grating distributed bragg reflector laser.  
   
   
       72 . A fiber optic communication system, comprising: 
 an optical signal source adapted to produce an optical power that is a partially frequency modulated signal;    an optical discriminator adapted to convert the partially frequency modulated signal into a substantially amplitude modulated signal that splits into a reflected signal and a transmissive signal; and    a wavelength locking circuit capable monitoring the optical signal source and the optical discriminator to compare a ratio between the optical power versus one of the reflected signal or the transmissive signal to substantially maintain the ratio constant.    
   
   
       73 . The system according to  claim 72 , further including: 
 a first photodiode capable of monitoring the optical power from the optical signal source; and    a second photodiode on a reflected side of the optical discriminator to detect the reflected signal, where the wavelength locking circuit is communicatably coupled to the first and second diodes to monitor the optical signal source and the reflected signal.    
   
   
       74 . The system according to  claim 72 , further including 
 a first photodiode capable of monitoring the optical power from the optical signal source; and    a second photodiode on a transmissive side of the optical discriminator to detect the transmissive signal, where the wavelength locking circuit is communicatably coupled to the first and second diodes to monitor the optical signal source and the reflected signal.    
   
   
       75 . The system according to  claim 72 , further including a thermo-electric cooler (TEC) coupled to the optical discriminator, where the wavelength locking circuit is communicateably coupled to the TEC to adjust the temperature of the optical power to keep the ratio substantially constant.  
   
   
       76 . A fiber optic communication system, comprising: 
 an optical signal source adapted to produce a partially frequency modulated signal; and    an optical discriminator adapted to convert the partially frequency modulated signal into a substantially amplitude modulated signal, where the optical discriminator is adapted to reflect a portion of the partially frequency modulated signal to produce a reflected signal that is used to wavelength lock the partially frequency modulated signal, and where the optical discriminator is adapted to compensate for at least a portion of a dispersion in a transmission fiber.    
   
   
       77 . The system according to  claim 76 , further including a wavelength locking circuit adapted to wavelength lock the partially frequency modulated signal by comparing the partially frequency modulated signal to the reflected signal and then adjusting the optical signal source to keep the ratio of the partially frequency modulated signal to the reflected signal substantially constant.  
   
   
       78 . The system according to  claim 76 , where the optical signal source is coupled to a thermo-electric cooler that adjust the temperature of the optical signal source to keep the ratio of the partially frequency modulated signal to the reflected signal substantially constant.  
   
   
       79 . A fiber optic communication system, comprising: 
 an optical signal source adapted to produce a partially frequency modulated signal; and    an optical discriminator adapted to convert the partially frequency modulated signal into a substantially amplitude modulated signal, where the optical discriminator is adapted to transmit a portion of the partially frequency modulated signal to produce a transmissive signal that is used to wave length lock the partially frequency modulated signal, and where the optical discriminator is adapted to compensate for at least a portion of a dispersion in a transmission fiber.    
   
   
       80 . The system according to  claim 79 , further including a wavelength locking circuit adapted to wavelength lock the partially frequency modulated signal by comparing the partially frequency modulated signal to the transmissive signal and then adjusting the optical signal source to keep the ratio of the partially frequency modulated signal to the transmissive signal substantially constant.  
   
   
       81 . The system according to  claim 79 , where the optical signal source is coupled to a thermo-electric cooler that adjust the temperature of the optical signal source to keep the ratio of the partially frequency modulated signal to the transmissive signal substantially constant.  
   
   
       82 . A fiber optic communication system, comprising: 
 an optical signal source for producing an optical signal;    a transmission medium having an associated dispersion D f ;    a frequency modulator between the optical signal source and the transmission medium adapted to at least partially frequency modulated the optical signal; and    an optical discriminator having an associated dispersion D d  adapted to convert the partially frequency modulated signal into a substantially amplitude modulated signal, where the associated dispersion D d  has either a positive or negative sign, where the sign D d  is an opposite sign of D f .    
   
   
       83 . The system according to  claim 82 , where the optical signal source is a continuous wave source.  
   
   
       84 . The system according to  claim 82 , where the optical signal source is externally modulated.  
   
   
       85 . The system according to  claim 82 , where the frequency modulator is a semiconductor optical amplifier.  
   
   
       86 . A fiber optic communication system, comprising: 
 an optical signal source adapted to produce a partially frequency modulated signal;    a first optical discriminator adapted to convert the partially frequency modulated signal into a substantially amplitude modulated signal; and    a second optical discriminator having an associated dispersion D d  adapted to receive the substantially amplitude modulated signal and compensate for at least a portion of a dispersion D f  in a transmission medium, where D d  is the opposite sign of D f .    
   
   
       87 . The system according to  claim 86 , where the first optical discriminator is a first coupled multi-cavity (CMC) filter having a first transmission function and a first dispersion, and the second optical discriminator is a second CMC filter having a second transmission function, where the first and second CMC filters have a combined transmission function that is substantially a product of the first and second transmission functions, and a combined dispersion that is substantially a sum of first dispersion and the associated dispersion D d  of the second optical discriminator.  
   
   
       88 . The system according to  claim 86 , where the optical signal source is a directly modulated laser.  
   
   
       89 . The system according to  claim 86 , where the second optical discriminator is adapted to reflect a portion of the substantially amplitude modulated signal to produce a reflected signal that is used to wavelength lock the partially frequency modulated signal.  
   
   
       90 . The system according to  claim 86 , where the second optical discriminator is a Gire-Tournois interferometer.  
   
   
       91 . The system according to  claim 86 , where the first optical discriminator is adapted to reflect a portion of the partially frequency modulated signal to produce a reflected signal that is used to wavelength lock the partially frequency modulated signal.  
   
   
       92 . The system according to  claim 86 , where the first optical discriminator is a multi-cavity etalon filter where the dispersion D d  of the second optical discriminator occurs at a multiplicity of equally spaced wavelengths.  
   
   
       93 . The system according to  claim 86 , where the first optical discriminator is a sampled Bragg grating filter.  
   
   
       94 . The system according to  claim 93 , where the sampled Bragg grating filter is formed in a fiber.  
   
   
       95 . The system according to  claim 93 , where the sampled Bragg grating filter is formed in a planar waveguide.  
   
   
       96 . The system according to  claim 86 , further including a wavelength locking circuit adapted to wavelength lock the partially frequency modulated signal by comparing the partially frequency modulated signal to a reflected signal and then adjusting the optical signal source to keep a ratio of the partially frequency modulated signal to the reflected signal substantially constant.  
   
   
       97 . A fiber optic communication system, comprising: 
 an optical signal source, where the optical signal source is adapted to produce a partially frequency modulated signal;    a plurality of cascading transmission filters capable of converting the partially frequency modulated signal to a substantially amplitude modulated signal; and    a reflective filter capable of compensating for at least a portion of the dispersion in a transmission fiber.    
   
   
       98 . The system according to  claim 97 , where the plurality of cascading transmission filters are multicavity thin film filters that are adapted to maintain their optical spectra substantially constant over temperature changes.  
   
   
       99 . The system according to  claim 97 , where the reflective filter is a Gire-Tournois interferometer.  
   
   
       100 . A method for transmitting optical signal through a transmission fiber, comprising: modulating an optical signal to a partially frequency modulated signal; 
 converting the partially frequency modulated signal to a substantially amplitude modulated signal; and    compensating for at least a portion of a dispersion in a transmission fiber to transmit further the optical signal through the transmission fiber.    
   
   
       101 . The method according to  claim 100 , where the modulating is done directly at a laser source that produces the partially frequency modulated signal.  
   
   
       102 . The method according to  claim 101 , where the laser source is a semiconductor laser, and further includes: 
 biasing the semiconductor laser high above its threshold to produce an extenuation.    
   
   
       103 . The method according to  claim 100 , where the compensating is done by providing dispersion that is opposite sign of the dispersion in the transmission fiber.  
   
   
       104 . The method according to  claim 100 , further including: 
 reflecting the frequency modulated signal to generate a negative dispersion to compensate for a positive dispersion in the transmission fiber.    
   
   
       105 . The method according to  claim 100 , further including: 
 comparing a ratio between a power of the optical signal versus a reflected portion of the optical signal; and    maintaining the ratio to substantially wavelength lock the optical signal.    
   
   
       106 . The method according to  claim 1 , where the step of modulating the optical signal is done by using a semiconductor laser.  
   
   
       107 . The method according to  claim 106 , further including: 
 comparing a ratio between a power of the optical signal versus a transmissive portion of the optical signal; and    maintaining the ratio to substantially wavelength lock the optical signal.    
   
   
       108 . The method according to  claim 107 , further including: 
 adjusting the temperature of the semiconductor laser to shift the wavelength of the optical signal to maintain the ratio substantially constant.    
   
   
       109 . The method according to  claim 100 , where the converting and compensating is done by a discriminator having a plurality of interfering single cavity filters that provide positive and negative transmission edges and a bandwidth, where each transmission edge has a slope.  
   
   
       110 . The method according to  claim 109 , where the discriminator is a coupled multi-cavity (CMC) filter.  
   
   
       111 . The method according to  claim 100 , further including cascading a plurality of non-interfering CMC filters to obtain a desirable compensating characteristics.  
   
   
       112 . A method for transmitting optical signal through a transmission fiber for a longer reach application, comprising: 
 generating a partially frequency modulated signal;    discriminating the partially frequency modulated signal to produce a substantially amplitude modulated signal; and    compensating for at least a portion of a dispersion in a transmission fiber.    
   
   
       113 . The method according to  claim 112 , where the generating is done directly at a laser source that produces the partially frequency modulated signal.  
   
   
       114 . The method according to  claim 112 , where the laser source is a semiconductor laser, and further including: 
 biasing the semiconductor laser high above its threshold to produce an extenuation.    
   
   
       115 . The method according to  claim 112 , where the discriminating compensates for the dispersion in the transmission fiber by providing dispersion in the discriminating that is opposite sign of the dispersion in the transmission fiber.  
   
   
       116 . The method according to  claim 112 , further including: 
 reflecting the frequency modulated signal to generate a negative dispersion to compensate for a positive dispersion in the transmission fiber.    
   
   
       117 . The method according to  claim 112 , where the discriminating is done by a plurality of interfering single cavity filters that provide positive and negative transmission edges and a bandwidth, where each transmission edge has a slope.  
   
   
       118 . The method according to  claim 112 , where the discriminating is done by a coupled multi-cavity filter.  
   
   
       119 . The method according to  claim 112 , further including cascading a plurality of non-interfering coupled multi-cavity filters to obtain a desirable compensating characteristics.  
   
   
       120 . A method for producing a frequency modulated signal, comprising: 
 alternating high and low refractive index mirrors to produce a distributed bragg reflector (DBR) mirrors;    sandwiching a gain medium between two DBR mirrors to provide a laser source;    combining a modulated signal source and a dc bias source to produce a combined signal; and    modulating the laser source with the combined signal to produce an optical signal that is biased above its threshold and frequency modulated.    
   
   
       121 . The method according to  claim 120 , where the modulating is done directly at the laser source.  
   
   
       122 . The method according to  claim 120 , where the modulating is done externally from the laser source.  
   
   
       123 . A method for producing a frequency modulated signal, comprising: 
 producing a laser;    biasing the laser above its threshold level; and    modulating frequency of the laser to produce at least a partially frequency modulated signal.    
   
   
       124 . The method according to  claim 123 , where the producing is done by a single wavelength semiconductor laser.  
   
   
       125 . The method according to  claim 123 , where the producing is done by a tunable semiconductor laser.  
   
   
       126 . The method according to  claim 123 , where the modulating is done directly at the producing laser.  
   
   
       127 . The method according to  claim 123 , where the modulating is done externally to the producing laser.  
   
   
       128 . The method according to  claim 123 , further including: 
 discriminating the partially frequency modulated signal to produce a substantially amplitude modulated signal; and    compensating for at least a portion of a dispersion in a transmission fiber.