Direct RF modulation on semiconductor lasers of wavelength 1310 nm has been widely applied to amplitude modulation vestigial side-band(AM-VSB)lightwave cable television (CATV) systems. The channel capacity is limited mainly by the nonlinear distortion of laser diode, which induces system performance degradation of composite second order (CSO) and composite triple beats (CTB). Though the linearity of laser diode has been improved during the fabrication process, carrier to noise ratio (CNR), CSO, and CTB were still degraded by increasing either RF output power level or the channel loading. Thus, some linearization techniques were proposed to extend the channel capacity. The predistortion approach is the simplest and the lowest cost one among the techniques. This paper describes a distortion compensation method with an electrical ¡§branch¡¨ circuit configuration, which is designed to reduce the nonlinear distortion induced by the laser diode. In this architecture, we utilize the method of impedance non-matching and the reflection of signals. According to the experiment results, we have found that before predistortion compensation, CNR / CSO / CTB are 51.6 dB / 62 dBc / 70 dBc, respectively. After compensation, CNR / CSO / CTB are 51.5 dB / 70 dBc / 71 dBc, respectively. Comparing with and without the distortion compensation, we found that CSO has an improvement with 8 dB, which reveals that the predistorion circuit improves the linearity of laser obviously. This study may give a guideline of predistortion technique and help to design optical transmitter.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0612101-215356 |
| Date | 12 June 2001 |
| Creators | Juang, Min-Shi |
| Contributors | T.Y.Chang, J. Hu, Tsair-Chun Liang, Yung-Kuang Chen |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0612101-215356 |
| Rights | restricted, Copyright information available at source archive |
Page generated in 0.0019 seconds