Method for estimating amount of wavelength dispersion, wavelength dispersion compensation circuit, and receiving device

A wavelength dispersion compensation circuit, comprising:

• an analog-digital convertor which converts optical analog waveform received from the optical fiber transmission path into a digital signal;
• a digital signal processor which compensates waveform distortion due to wavelength dispersion at the optical fiber transmission path of the digital signal output from the analog-digital convertor with the dispersion compensation amount estimated with a wavelength dispersion amount estimation method to estimate a dispersion compensation amount for compensating waveform distortion due to wavelength dispersion at an optical fiber transmission path;
• and
• a symbol clock extractor which extracts a symbol arrival timing clock of received data included in the digital signal output from the analog-digital convertor and outputs strength of the symbol arrival timing clock as the clock detection value,
• the wavelength dispersion amount estimation method is comprising:
• an initial value setting step to set a dispersion compensation amount D(0) which is an initial value (k=0) of a kth dispersion compensation amount D(k) (k is an integer);
• a clock detecting step to detect and store strength of a symbol arrival timing clock included in received data at the dispersion compensation amount D(k) as a clock detection value S(k);
• a plus side shifting step to detect and store strength of the symbol arrival timing clock at a dispersion compensation amount D(k)+ΔD which is obtained by shifting the dispersion compensation amount D(k) to a plus side by a specific amount ΔD as a clock detection value S(k+);
• a minus side shifting step to detect and store strength of the symbol arrival timing clock at a dispersion compensation amount D(k)−ΔD which is obtained by shifting the dispersion compensation amount D(k) to a minus side by the specific amount ΔD as a clock detection value S(k−);
• a comparing step to compare the clock detection value S(k), the clock detection value S(k+), and the clock detection value S(k−);
• and
• an evaluating step to determine to complete estimation of the dispersion Compensation amount as determining the dispersion compensation amount D(k) as an optimum dispersion compensation amount when the clock detection value S(k) is the largest, and to perform the clock detecting step, the plus side shifting step, the minus side shifting step, and the comparing step once again with the dispersion compensation amount of the largest clock detection value set as a k+1th dispersion compensation amount D(k+1) when the clock detection value S(k+) or the clock detection value S(k−) is the largest, as a result of the comparing step.

A receiving device, comprising the wavelength dispersion compensation circuit which is comprising:

• an analog-digital convertor which converts optical analog waveform received from the optical fiber transmission path into a digital signal;
• a digital signal processor which compensates waveform distortion due to wavelength dispersion at the optical fiber transmission path of the digital signal output from the analog-digital convertor with the dispersion compensation amount estimated with a wavelength dispersion amount estimation method to estimate a dispersion compensation amount for compensating waveform distortion due to wavelength dispersion at an optical fiber transmission path;
• and
• a symbol clock extractor which extracts a symbol arrival timing clock of received data included in the digital signal output from the analog-digital convertor and outputs strength of the symbol arrival timing clock as the clock detection value,
• the wavelength dispersion amount estimation method is comprising:
• an initial value setting step to set a dispersion compensation amount D(0) which is an initial value (k=0) of a kth dispersion compensation amount D(k) (k is an integer);
• a clock detecting step to detect and store strength of a symbol arrival timing clock included in received data at the dispersion compensation amount D(k) as a clock detection value S(k);
• a plus side shifting step to detect and store strength of the symbol arrival timing clock at a dispersion compensation amount D(k)+ΔD which is obtained by shifting the dispersion compensation amount D(k) to a plus side by a specific amount ΔD as a clock detection value S(k+);
• a minus side shifting step to detect and store strength of the symbol arrival timing clock at a dispersion compensation amount D(k)−ΔD which is obtained by shifting the dispersion compensation amount D(k) to a minus side by the specific amount ΔD as a clock detection value S(k−);
• a comparing step to compare the clock detection value S(k), the clock detection value S(k+), and the clock detection value S(k−);
• and
• an evaluating step to determine to complete estimation of the dispersion compensation amount as determining the dispersion compensation amount D(k) as an optimum dispersion compensation amount when the clock detection value S(k) is the largest, and to perform the clock detecting step, the plus side shifting step, the minus side shifting step, and the comparing step once again with the dispersion compensation amount of the largest clock detection value set as a k+1th dispersion compensation amount D(k+1) when the clock detection value S(k+) or the clock detection value S(k−) is the largest, as a result of the comparing step.