Distributed antenna system for transmitting service signal and management control signal in 5G mobile communication system, and remote unit thereof

An optical repeater system comprising:

• a master unit connected to a base station;
• and
• a plurality of remote units connected to the master unit in a cascade configuration,
• wherein the plurality of remote units include a first remote unit directly connected to the master unit by an optical cable and a second remote unit directly connected to the first remote unit by another optical cable,
• wherein the master unit is configured to:
• receive a downlink electric signal from the base station,
• convert the received downlink electric signal into a downlink optical signal of a first wavelength,
• transmit the converted downlink optical signal to the plurality of remote units through the first remote unit,
• receive an uplink optical signal of a second wavelength from the plurality of remote units through the first remote unit,
• convert the received uplink optical signal into an uplink electric signal, and
• output the converted uplink electric signal to the base station, and
• wherein each of the remote units is configured to:
• receive the downlink optical signal from the master unit or a previous remote unit connected thereto,
• divide the received downlink optical signal into first and second downlink electric signals,
• output the first downlink electric signal to an antenna,
• transmit the second downlink electric signal to a subsequent remote unit connected thereto,
• receive a first uplink electric signal from the antenna,
• receive an uplink optical signal from the subsequent remote unit,
• convert the received uplink optical signal into a second uplink electric signal,
• combine the first and second uplink electric signals,
• convert the combined uplink electric signal into the uplink optical signal, and
• transmit the converted uplink optical signal to the master unit or the previous remote unit,
• wherein each of the plurality of remote units includes:
• a first analog circuit including:
• a first photodiode configured to convert the downlink optical signal into the downlink electric signal,
• a second photodiode configured to convert the uplink optical signal into the second uplink electric signal,
• a first laser diode configured to convert the uplink electric signal into the uplink optical signal,
• a second laser diode configured to convert the second downlink electric signal into the downlink optical signal,
• a signal distributor configured to divide the downlink electric signal into the first and second downlink electric signals, and
• a signal synthesizer configured to combine the first uplink electric signal received from the antenna and the second uplink electric signal received from the second photodiode into the uplink electric signal,
• a first wavelength division multiplexer (WDM) disposed between the master unit or the previous remote unit and both the first photodiode and the first laser diode and configured to wavelength-divide each of the uplink optical signal and the downlink optical signal, and
• a second WDM disposed between the subsequent remote unit and both the second photodiode and the second laser diode and configured to wavelength-divide each of the uplink optical signal and the downlink optical signal.