Two-dimensional optical CDMA system, PN coded wavelength/time encoder and decoder therein, and method of encoding/decoding

An encoder included in each of a plurality of user terminals connected to a base station, in which the plurality of user terminals are included in an OCDMA system, comprising:

• time domain encoding means for creating a time domain code having a sequence according to inputted data bits or a complementary code which is complementary to the time domain code;
• optical modulation means for selectively outputting lights, in which the lights are incident upon the optical modulation means from the outside, to two output leads, respectively, according to a chip bit of the time domain code or the complementary code;
• and
• wavelength domain encoding means for generating a two-dimensional code by encoding the light outputted from the first output lead of the optical modulation means into a wavelength domain sequence and the complementary two-dimensional code which is complementary to the two-dimensional code by encoding the light outputted from the second output lead of the optical modulation means into a complementary sequence of the wavelength domain sequence, and transmitting the two-dimensional code and the complementary two-dimensional code to the base station,
• wherein the two-dimensional code is a matrix type code generated from two different PN sequences including a time domain PN sequence in a first dimension and a wavelength domain PN sequence in a second dimension.

A decoder decoding two-dimensional codes of optical signals, which are sequentially encoded in time domain and in wavelength domain and then transmitted by the base station, comprising:

• wavelength decoding means for receiving the two dimensional codes, and decoding the two-dimensional codes in the wavelength domain to electric signals to be outputted;
• time domain decoding means for decoding the electric signals in the time domain;
• and
• threshold determination means for determining whether the decoded signal in the time domain decoding means is a threshold, and outputting data bits based on the determination,
• wherein the two-dimensional code is a matrix type code generated from two different PN sequences including a time domain PN sequence in a first dimension and a wavelength domain PN sequence in a second dimension.

A method of encoding/decoding data bits in an OCDMA system including a plurality of user terminals connected to a base station, comprising the steps of:

• generating a time domain code having a sequence according to the data bits or a complementary code which is complementary to the time domain code, and encoding the data bits in time domain, based on the generation;
• transmitting two dimensional code or a complementary code of the two dimensional code, in which the two dimensional code is generated as light inputted from the outside is encoded into a wavelength domain sequence and the complementary code is generated as the inputted light is encoded into a complementary sequence of the wavelength domain sequence, according to chip bits of the time domain code or the complementary code which is complementary to the time domain code;
• receiving the encoded light signal from a network and decoding it in the wavelength domain to an electric signal to be outputted;
• decoding the electric signal in the time domain;
• and
• determining whether the decoded signal decoded in the time domain is a threshold and outputting data bits thereto,
• wherein the two-dimensional code is a matrix type code generated from two different PN sequences including a time domain PN sequence in a first dimension and a wavelength domain PN sequence in a second dimension.