| 摘要 |
An improved analog VCSEL optical link includes the following elements listed in their downstream order from the input to the output: an RF preamplifier (A1) for receiving a bandpass RF signal; a first impedance matching network (LASINT) to match the input impedance of a downstream VCSEL laser to the output impedance of the RF preamplifier (A1); the VCSEL laser coupled to one end of a multimode optical fibre of given length for transducing optically the electrical bandpass RF signal; a PIN diode coupled to the other end of the multimode optical fibre for transducing into electrical the optical signal coming from the fibre; a second impedance matching network (C2, L2) to match the output impedance of the PIN diode to the input impedance of a downstream low-noise transimpedance amplifier (T1) and minimise the noise figure of said transimpedance amplifier (T1) in the meanwhile; the transimpedance amplifier (T1) including a low-noise FET in common source configuration; an RF power amplifier (A2); an RF signal envelope detector generating a control signal for a variable phase shifter placed downstream the RF power amplifier (A2) to compensate for the AM/PM distortion introduced by both the optical fibre and the power amplifier itself; and, if necessary, a gain linearisation network of the RF power amplifier (A2) and/or the RF preamplifier (A1). The analog VCSEL optical link is suitable for the following uses: connecting indoor apparatuses with tower antennas either static, i.e. point-to-point radio relay, or directive arrays, i.e. point-to-multipoint systems; building-up a fibre infrastructure for connecting centralised base stations with respective pool of remote antennas serving as many cells of a cellular telephone system such as: PCS, GSM, UMTS, and similar; intra-building connections for distributing, CATV services (fig.4). <IMAGE> |
