| 摘要 |
Optical distributed antenna systems comprising a head-end unit adapted to transmit downlink a modulated optical signal with wavelength lambda0 and N un-modulated optical signals with wavelength lambdaNu and N remote units (RU) and including at least one circulator. In some embodiments, an HE unit includes an arrangement of a single circulator coupled to a single detector of different optical wavelength carriers, the arrangement preventing beating. In some embodiments, a RU includes a reflective electro-absorption transceiver (REAT) which includes a single optical interface and a single RF port. The REAT detects the optical signal with lambda0 and converts it into a RF signal. The REAT also reflects an un-modulated optical signal with one of the wavelengths lambdaNu and provides a modulated uplink optical signal based on a RF signal. In some embodiments, a RU is configured as an optical antenna unit. In some embodiments, a plurality of RUs is combined with passive optical distribution units to provide hierarchical DAS architectures. |
