Method of coding signal for digital optical communication having spectrum which attains zero level at prescribed frequency within main lobe band, baseband transmitter or ASK transmitter using such method, and baseband receiver or ASK receiver decoding signal coded by such method

A baseband receiver using a symbol formed of N slots [s1, s2, s3, . . . , sN], wherein si is either 0 or 1 where i is an integer and 1≦i≦N, comprising:

• O/E conversion means for converting a received optical signal pattern into a symbol pattern;
• and
• decoding means for decoding said symbol pattern based on a plurality of symbols which satisfy the following expression and generating received data, wherein k is an arbitrary positive integer, and p1, q1, p2, q2, . . . , pk and qk are integers which satisfy 1≦p1<q1, 1≦p2<q2, . . . , 1≦pk<qk, and p1/q1<p2/q2<. . . <pk/qk:
• 32 ∑ i = 1 N ⁢ s i ⁢ { cos ⁡ ( 2 ⁢ π ⁢ ⁢ P 1 q 1 ⁢ ( i - 1 ) ) - cos ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P 1 q 1 ⁢ i ) } = 0 ∑ i = 1 N ⁢ s i ⁢ { sin ⁡ ( 2 ⁢ π ⁢ ⁢ P 1 q 1 ⁢ i ) - sin ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P 1 q 1 ⁢ ( i - 1 ) ) } = 0 ∑ i = 1 N ⁢ s i ⁢ { cos ⁡ ( 2 ⁢ π ⁢ ⁢ P 2 q 2 ⁢ ( i - 1 ) ) - cos ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P 2 q 2 ⁢ i ) } = 0 ∑ i = 1 N ⁢ s i ⁢ { sin ⁡ ( 2 ⁢ π ⁢ ⁢ P 2 q 2 ⁢ i ) - sin ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P 2 q 2 ⁢ ( i - 1 ) ) } = 0 ⁢ ⋮ ∑ i = 1 N ⁢ s i ⁢ { cos ⁡ ( 2 ⁢ π ⁢ ⁢ P k q k ⁢ ( i - 1 ) ) - cos ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P k q k ⁢ i ) } = 0 ∑ i = 1 N ⁢ s i ⁢ { sin ⁡ ( 2 ⁢ π ⁢ ⁢ P k q k ⁢ i ) - sin ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P k q k ⁢ ( i - 1 ) ) } = 0 ) . ( 1 )

An ASK optical transmitter using a symbol formed of N slots [s1, s2, s3, . . . , sN], wherein si is either 0 or 1 where i is an integer and 1≦i≦N, comprising:

• coding means for coding transmission data based on a plurality of symbols which satisfy the following expression and outputting the coded data as a symbol pattern, wherein k is an arbitrary positive integer, and p1, q1, p2, q2. . . , pk and qk are integers which satisfy 1≦p1<q1, 1≦p2<q2, . . . , 1≦pk<qk, and p1/q1<p2/q2<. . . pk/qk:
• 33 ∑ i = 1 N ⁢ s i ⁢ { cos ⁡ ( 2 ⁢ π ⁢ ⁢ P 1 q 1 ⁢ ( i - 1 ) ) - cos ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P 1 q 1 ⁢ i ) } = 0 ∑ i = 1 N ⁢ s i ⁢ { sin ⁡ ( 2 ⁢ π ⁢ ⁢ P 1 q 1 ⁢ i ) - sin ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P 1 q 1 ⁢ ( i - 1 ) ) } = 0 ∑ i = 1 N ⁢ s i ⁢ { cos ⁡ ( 2 ⁢ π ⁢ ⁢ P 2 q 2 ⁢ ( i - 1 ) ) - cos ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P 2 q 2 ⁢ i ) } = 0 ∑ i = 1 N ⁢ s i ⁢ { sin ⁡ ( 2 ⁢ π ⁢ ⁢ P 2 q 2 ⁢ i ) - sin ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P 2 q 2 ⁢ ( i - 1 ) ) } = 0 ⁢ ⋮ ∑ i = 1 N ⁢ s i ⁢ { cos ⁡ ( 2 ⁢ π ⁢ ⁢ P k q k ⁢ ( i - 1 ) ) - cos ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P k q k ⁢ i ) } = 0 ∑ i = 1 N ⁢ s i ⁢ { sin ⁡ ( 2 ⁢ π ⁢ ⁢ P k q k ⁢ i ) - sin ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P k q k ⁢ ( i - 1 ) ) } = 0 ) ( 1 )
• modulation means for superposing a subcarrier on the symbol pattern output by said coding means and generating an electrical signal pattern;
• and
• E/O conversion means for converting the electrical signal pattern generated by said modulation means into an optical signal.

An ASK optical receiver using a symbol formed of N slots [s1, s2, s3, . . . , sN], wherein si is either 0 or 1 where i is an integer and 1≦i≦N, comprising:

• O/E conversion means for converting a received optical signal pattern into an electrical signal pattern;
• detection means for detecting said electrical signal pattern and generating a symbol pattern;
• and
• decoding means for decoding said symbol pattern based on a plurality of symbols which satisfy the following expression and generating received data, wherein k is an arbitrary positive integer, and p1, q1, p2, q2, . . . , pk and qk, are integers which satisfy 1≦p1<q1, 1≦p2<q2, . . . , 1pk<qk, and p1/q1<p2/q2<. . . <pk/qk:
• 34 ∑ i = 1 N ⁢ s i ⁢ { cos ⁡ ( 2 ⁢ π ⁢ ⁢ P 1 q 1 ⁢ ( i - 1 ) ) - cos ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P 1 q 1 ⁢ i ) } = 0 ∑ i = 1 N ⁢ s i ⁢ { sin ⁡ ( 2 ⁢ π ⁢ ⁢ P 1 q 1 ⁢ i ) - sin ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P 1 q 1 ⁢ ( i - 1 ) ) } = 0 ∑ i = 1 N ⁢ s i ⁢ { cos ⁡ ( 2 ⁢ π ⁢ ⁢ P 2 q 2 ⁢ ( i - 1 ) ) - cos ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P 2 q 2 ⁢ i ) } = 0 ∑ i = 1 N ⁢ s i ⁢ { sin ⁡ ( 2 ⁢ π ⁢ ⁢ P 2 q 2 ⁢ i ) - sin ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P 2 q 2 ⁢ ( i - 1 ) ) } = 0 ⁢ ⋮ ∑ i = 1 N ⁢ s i ⁢ { cos ⁡ ( 2 ⁢ π ⁢ ⁢ P k q k ⁢ ( i - 1 ) ) - cos ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P k q k ⁢ i ) } = 0 ∑ i = 1 N ⁢ s i ⁢ { sin ⁡ ( 2 ⁢ π ⁢ ⁢ P k q k ⁢ i ) - sin ⁢ ⁢ ( 2 ⁢ π ⁢ ⁢ P k q k ⁢ ( i - 1 ) ) } = 0 ) ( 1 )