Abstract: A device in accordance with the invention uses a novel four-port wavelength-division multiplexing (WDM) filter and a single erbium-doped optical amplifier (EDFA) to implement a dual wavelength bi-directional (single fiber) optical amplifier module. A system using an amplifier module in accordance with the invention, advantageously allows communication network managers to simultaneously reduce the cost of signal amplification hardware across a fiber optic network, increase fiber utilization, simplify field installation and maintenance operations, and maintain adherence to conventional protection philosophies such as "one system per fiber.

Abstract: There is provided an optical circulator (16) for bidirectional communication on a fiber optic communication transmission system. Polarization preserving single-mode fiber lengths (26), (28) connect all-fiber polarization splitter (18) with the Faraday single-mode fiber lengths (22), (24). Polarization preserving single-mode fiber lengths (30), (32) connect the opposite ends of Faraday single-mode fiber lengths (22), (24) with all-fiber polarization splitter (20). A communication transmitter is connected to splitter (18) at port 1, and a communication receiver is connected to splitter (18) at port 3. A fiber optic communication link (50) is connected to splitter (20) at port 2. The components of optical circulator (16) cooperate such that light transmitted into port 1 exits from port 2, and light transmitted into port 2 exits from port 3.

Abstract: A data dial system having at least one matrix switch, one or more user terminals, one or more Touch-Tone push button telephones, and at least one processor. The matrix switch can switch the user terminals between various inputs and outputs. The Touch-Tone push button telephones, each of which has a dual-tone-multiple-frequency keypad, generates signals which can actuate the processor. The processor controls the operation of the matrix switch, for switching signals between signal sources and signal destinations by establishing connections and by performing disconnections of the various inputs and outputs of the matrix switch.

Abstract: There is provided an optical circulator (16) for bidirectional communication on a fiber optic communication transmission system. A reflection rhomb (17) includes a polarizing thin film (26) and an inclined, internally reflecting end surface (22). A first birefringent crystal (28) is disposed against the reflection rhomb (17). A quartz rotator (34) is disposed against the opposite side of the first birefringent crystal (28). A Faraday rotator (40) is disposed against the opposite side of the quartz rotator (34). A second birefringent crystal (46) is disposed against the opposite side of the Faraday rotator (40). The components of optical circulator (16) cooperate such that light transmitted into port 1 exits from port 2, and light transmitted into port 2 exits from port 3.