A comparative study of the performance of seven- and 63-chip optical code-division multiple-access encoders and decoders based on superstructured fiber Bragg gratings

We report a range of elementary optical coding and decoding experiments employing superstructured fiber Bragg grating (SSFBG) components. First, we perform a comparative study of the relative merits of bipolar and unipolar coding:decoding schemes and show that the SSFBG approach allows high-quality unipolar and bipolar coding. A performance close to that theoretically predicted for seven-chip, 160-Gchip/s M-sequence codes is obtained. Second, we report the fabrication and performance of 63-chip, 160-Gchip/s, bipolar Gold sequence grating pairs. These codes are at least eight times longer than those generated by any other scheme based on fiber grating technology so far reported. Last, we describe a range of transmission system experiments for both the seven- and 63-bit bipolar grating pairs. Error-free performance is obtained over transmission distances of similar to 25 km of standard fiber. In addition, we have demonstrated error-free performance under multiuser operation (two simultaneous users). Our results highlight the precision and flexibility of our particular grating writing process and show that SSFBG technology represents a promising technology not just for optical code division multiple access (OCDMA) but also for an extended range of other pulse-shaping optical processing applications.