Optical repeater having loop-back function used in transmission system

An optical repeater having a loop-back function used in a transmission system including first and second transmission lines, comprising:

• a first optical amplifier, connected to said first transmission line, for directly amplifying optical signals transferred from a first terminal station through said first transmission line;
• a second optical amplifier, connected to said second transmission line, for directly amplifying optical signals transferred from a second terminal station through said second transmission line;
• a loop-back means, connected to said first and second transmission lines, for constituting a loop-back line;
• and
• a control means, connected to said first and second amplifiers and said loop-back means, for controlling said loop-back means to constitute the loop-back line when detecting a loop-back instruction output from one of said terminal stations through a corresponding one of said optical amplifiers,
• wherein said loop back means comprises first and second optical line shutters, first and second optical mixers, first and second optical loop shutters, and first and second optical splitters;
• and wherein said first optical line shutter, said first optical mixer, said first optical amplifier, and said first optical splitter are provided in series along said first transmission line, and said second optical line shutter, said second optical mixer, said second optical amplifier, and said second optical splitter are provided in series along said second transmission line.

An optical repeater having a loop-back function used in a transmission system including first and second transmission lines, comprising:

• a first optical amplifier, connected to said first transmission line, for directly amplifying optical signals transferred from a first terminal station through said first transmission line;
• a second optical amplifier, connected to said second transmission line, for directly amplifying optical signals transferred from a second terminal station through said second transmission line;
• a loop-back means, connected to said first and second transmission lines, for constituting a loop-back line;
• and
• a control means, connected to said first and second amplifiers and said loop-back means, for controlling said loop-back means to constitute the loop-back line when detecting a loop-back instruction output from one of said terminal stations through a corresponding one of said optical amplifiers,
• wherein said loop back means comprises first and second optical line shutters, first and second optical mixers, first and second optical loop shutters, and first and second optical splitters;
• and wherein said first optical mixer, said first optical amplifier, said first optical splitter, and said first optical line shutter are provided in series along said first transmission line, and said second optical mixer, said second optical amplifier, said second optical splitter, and said second optical line shutter are provided in series along said second transmission line.

An optical repeater having a loop-back function used in a transmission system including first and second transmission lines, comprising:

• a first optical amplifier, connected to said first transmission line, for directly amplifying optical signals transferred from a first terminal station through said first transmission line;
• a second optical amplifier, connected to said second transmission line, for directly amplifying optical signals transferred from a second terminal station through said second transmission line;
• a loop-back means, connected to said first and second transmission lines, for constituting a loop-back line;
• and
• a control means, connected to said first and second amplifiers and said loop-back means, for controlling said loop-back means to constitute the loop-back line when detecting a loop-back instruction output from one of said terminal stations through a corresponding one of said optical amplifiers,
• wherein said loop back means comprises first and second optical mixers, first and second optical splitters, and first and second optical loop shutters;
• wherein said first optical mixer, said first optical amplifier, and said first optical splitter are provided in series along said first transmission line, and said second optical mixer, said second optical amplifier, and said second optical splitter are provided in series along said second transmission line.

An optical repeater having a loop-back function used in a transmission system including first and second transmission lines, comprising:

• a first optical amplifier, connected to said first transmission line, for directly amplifying optical signals transferred from a first terminal station through said first transmission line;
• a second optical amplifier, connected to said second transmission line, for directly amplifying optical signals transferred from a second terminal station through said second transmission line;
• a loop-back means, connected to said first and second transmission lines, for constituting a loop-back line;
• and
• a control means, connected to said first and second amplifiers and said loop-back means, for controlling said loop-back means to constitute the loop-back line when detecting a loop-back instruction output from one of said terminal stations through a corresponding one of said optical amplifiers,
• wherein each optical amplifier comprises an optical mixer for adding pump light to the optical signals, erbium-doped optical fibers, an optical splitter for branching the optical signals from said fibers, an opto-electrical conversion unit for converting the optical signals to electrical signals, an auto gain control circuit for automatically controlling the gain of signals output from said opto-electrical conversion unit, and a laser diode for generating the pump light in accordance with electrical output signals of said auto gain control circuit.

An optical repeater having a loop-back function used in a transmission system including first and second transmission lines, comprising:

• a first optical amplifier, connected to said first transmission line, for directly amplifying optical signals transferred from a first terminal station through said first transmission line;
• a second optical amplifier, connected to said second transmission line, for directly amplifying optical signals transferred from a second terminal station through said second transmission line;
• a loop-back means, connected to said first and second transmission lines, for constituting a loop-back line;
• and
• a control means, connected to said first and second amplifiers and said loop-back means, for controlling said loop-back means to constitute the loop-back line when detecting a loop-back instruction output from one of said terminal stations through a corresponding one of said optical amplifiers,
• wherein said control means is constituted by first and second bandpass filters, for picking up supervisory signals from electrical signals output from said opto-electrical conversion units, and first and second supervisory units, for amplitude-modulating optical output of said laser diode by receiving the supervisory signals from said bandpass filters.