Abstract: A laser apparatus, which generates laser light to be transmitted through an optical transmission system includes a laser that emits light that is substantially linearly polarized, a housing in which the laser is mounted, and a quarter wave retarder plate. The quarter wave retarder plate is disposed so that the emitted laser light passes through the quarter wave retarder plate prior to transmission of the emitted laser light through the optical transmission system. The quarter wave retarder plate causing the emitted laser light to become circularly polarized with a predefined handedness. The quarter wave retarder plate is also disposed so that light reflected by the optical transmission system back toward the laser passes through the quarter wave retarder plate a second time prior to reaching the laser, causing the reflected light to become linearly polarized with a linear polarization that is orthogonal to the polarization state of the light emitted by the laser.

Abstract: A hand-held circular saw which is characterized by a gasoline-powered, trigger-operated blade drive unit connected to a conventional circular saw by means of a specially-designed adaptor. In a preferred embodiment the circular saw is characterized by a circular saw blade rotatably mounted in a saw housing which is connected to a drive shaft housing and adjacent gear housing. The adaptor is secured inside the drive shaft housing, and the blade drive shaft extends from connection to a blade-driving gear train inside the gear housing, and through the adaptor and projects from the drive shaft housing. The blade drive unit receives the protruding blade drive shaft, and is fitted with an attachment collar which removably receives the adaptor to connect the blade drive unit to the circular saw. The gasoline-powered circular saw is lightweight, efficient and suitable for outdoor home, farm or commercial use.

Abstract: A dual optical fiber transceiver, for use with first and second optical fibers, includes a laser transmitter for transmitting laser light into the first optical fiber, a laser light receiver for receiving laser light from the second optical fiber, and a controller coupled to the laser transmitter and laser light receiver. The controller includes a multi-protocol state machine for establishing the full duplex connection whenever the other device operates in compliance with either (A) a predefined "on-off-on" signaling protocol for establishing full duplex connections, or (B) a second predefined signaling protocol for establishing full duplex connections. In a preferred embodiment, the predefined "on-off-on" signaling protocol is the Open Fiber Control (OFC) protocol and the second predefined signaling protocol is a standard "laser transmitter always on" protocol.