Telecommunications system simultaneously receiving and modulating an optical signal

A radio or microwave distribution point or base station comprising:

• an electro-absorption modulator having an optical input port, an optical output port and electrical contacts for the application of electrical control signals to the modulator;
• first antenna means for the reception of free space transmissions of radio frquency or microwave signals;
• second antenna means for the free space transmission of radio frequency or microwave signals;
• an optical input port for connection to an optical fibre feed to receive an optical input and to feed it to the input port of the modulator;
• an optical output port for connection to an output optical fibre to pass thereto optical signals from the output port of the modulator;
• wherein said first antenna means is operatively connected to the electrical contacts of the modulator to permit the application of radio frequency or microwave signals received by the first antenna means to the electrical contacts of the modulator to cause an optical input received at the input port of the modulator to be output from the output port of the modulator carrying a modulation imposed by the modulator;
• and wherein the second antenna means is operatively connected to the electrical contacts of the modulator to output a radio frequency or microwave signal produced by modulator as the result of the receipt by the modulator of an optical input signal at the optical input port of the modulator.

An antenna installation for a radio transmission system, the installation comprising:

• antenna means for transmission and reception of radio-frequency signals;
• optical input and optical output ports;
• an electro-absorption modulator arranged in the optical path between the optical input port and the output port and operatively connected to the antenna means and arranged in use to receive RF signals therefrom and to impose a corresponding modulating onto light received via said input port and which passes to said output port;
• and optical detection means arranged in use to receive optical signals via said input port and operatively connected to the antenna means so that RF modulation present in said optical signals is coupled out to said antenna means from which it is then radiated.

A cellular radio system comprising:

• first and second plurality of base stations, at least one of the plurality of base stations includes:
• an electro-absorption modulator having an optical input port, an optical output port and electrical contacts for the application of electrical control signals to the modulator;
• first antenna means for the reception of free space transmissions of radio frequency or microwave signals;
• second antenna means for the free space transmission of radio frequency or microwave signals;
• an optical input port for connection to an optical fibre feed to receive an optical input and to feed it to the input port of the modulator;
• an optical output port for connection to an output optical fibre to pass thereto optical signals from the output port of the modulator;
• said first antenna means being operatively connected to the electrical contacts of the modulator to permit the application of radio frequency or microwave signals received by the first antenna means to the electrical contacts of the modulator to cause an optical input received at the input port of the modulator to be output from the output port of the modulator carrying a modulation imposed by the modulator;
• and
• the second antenna means being operatively connected to the electrical contacts of the modulator to output a radio frequency or microwave signal produced by the modulator as the result of the receipt by the modulator of an optical input signal at the optical input port of the modulator;
• the first and second plurality serving distinct geographical areas;
• optical source means including an optical carrier generator and means to impose radio frequency signals onto an optical carrier;
• a first group of one or more optical fibre links to supply the optical carrier and the imposed radio frequency signals to said first plurality of base stations;
• a second group of one or more optical fibre links to supply the optical carrier and the imposed radio frequency signals to said second plurality of base stations;
• and
• switching means selectively to switch said carrier between the first and second group of fibre links and hence between said first and second plurality of base stations;
• wherein the optical source means is shared between the first and second plurality of base stations by switching between said first and second group of fibre links in accordance with the actual or predicted level of demand on the relevant plurality of base stations.