Transmitter Frequency Peaking for Optical Fiber Channels

Abstract

Frequency peaking is used in the transmitter to improve link performance. In one example, frequency peaking improves the PIE D or TWDP. The frequency peaking can result in pulse shapes that have more electrical energy in the receiver (and therefore higher received SNR) than uncompensated pulses. In addition, due to the response of typical fibers, boosting the high frequencies typically will flatten the received spectrum, which will improve the performance of the equalizer in an EDC receiver.

1 . An optical transmitter for transmitting data over an optical fiber at a specified data rate, wherein the optical transmitter comprises:
 a laser that exhibits relaxation oscillation; and   a laser driver coupled to drive the laser, the laser driver adapted to utilize the laser relaxation oscillation to boost the peak frequency relative to a DC frequency; wherein the laser produces an optical signal that encodes the data and is suitable for transmission over the optical fiber, and the optical signal has a frequency spectrum that has a relative peak at a peak frequency located in a vicinity of a line rate and the relative peak is relative to a reference frequency spectrum of a reference optical signal produced by an ideal rectangular pulse transmitter encoding the data.   
     
     
         2 . The transmitter of  claim 1  wherein the peak frequency is between 10% and 100% of the line rate. 
     
     
         3 . The transmitter of  claim 1  wherein the peak frequency is between 25% and 75% of the line rate. 
     
     
         4 . The transmitter of  claim 1  wherein the peak frequency is approximately 35-50% of the line rate. 
     
     
         5 . The transmitter of  claim 1  wherein the optical pulses encode the data based on on-off keying. 
     
     
         6 . The transmitter of  claim 1  wherein the data rate is approximately 10 G. 
     
     
         7 . The transmitter of  claim 1  wherein the transmitter complies with a standard specifying a maximum power penalty. 
     
     
         8 . The transmitter of  claim 1  wherein the transmitter has a lower power penalty than the ideal rectangular pulse transmitter. 
     
     
         9 . The transmitter of  claim 1  wherein the transmitter has a lower PIE-D power penalty than the ideal rectangular pulse transmitter. 
     
     
         10 . The transmitter of  claim 1  wherein the peak frequency is located in a frequency band that is attenuated by the optical fiber. 
     
     
         11 . The transmitter of  claim 1  wherein the optical pulses are characterized by overshoot at the frequency peak. 
     
     
         12 . The transmitter of  claim 1  wherein the transmitter complies with an X2, XFP or SFP+ form factor. 
     
     
         13 . A method for transmitting data over an optical fiber at a specified data rate, the method comprising:
 receiving the data; and   producing an optical signal that encodes the data and is suitable for transmission over the optical fiber, wherein the optical signal has a frequency spectrum that has a relative peak at a peak frequency located in a vicinity of a line rate and the relative peak is relative to a reference frequency spectrum of a reference optical signal produced by an ideal rectangular pulse transmitter encoding the data, wherein the step of producing the optical signal comprises utilizing a laser relaxation oscillation to boost the peak frequency relative to a DC frequency.   
     
     
         14 . The method of  claim 13  wherein the peak frequency is between 10% and 100% of the line rate. 
     
     
         15 . The method of  claim 13  wherein the peak frequency is between 25% and 75% of the line rate. 
     
     
         16 . The method of  claim 13  wherein the step of producing the optical signal comprises producing the optical pulses based on on-off keying of the data. 
     
     
         17 . The method of  claim 13  wherein the data rate is approximately 10 G. 
     
     
         18 . The method of  claim 13  wherein the optical signal has a lower power penalty than the ideal rectangular pulse transmitter. 
     
     
         19 . The method of  claim 13  wherein the peak frequency is located in a frequency band that is attenuated by the optical fiber.