Abstract: A rapid and reconfigurable deployment of services in a CATV system is enabled by the use of dynamic passive optical networks (DPONs) in accordance with the present invention. By delivering a number of wavelengths to the PON and using various dynamically reconfigurable groupings of the wavelengths to support differing subsets of users, the maximum capabilities of a static PON architecture are greatly exceeded. In accordance with one embodiment of the invention, the dynamic PON device accepts M wavelengths on a single optical fiber. The output of the dynamic PON device includes N output ports. Each of the M signals can be delivered to none, some or all of the N output ports. At its input, the DPON includes an optical amplifier for amplifying the multi-wavelength input signal to a desired power level prior to splitting. A 1:N channel power splitter couples to the output of the optical amplifier. Each of the power splitter outputs contains all M wavelength channels of the optical fiber.

Abstract: A rapid and reconfigurable deployment of services in a CATV system is enabled by the use of dynamic passive optical networks (DPONs) in accordance with the present invention. By delivering a number of wavelengths to the PON and using various dynamically reconfigurable groupings of the wavelengths to support differing subsets of users, the maximum capabilities of a static PON architecture are greatly exceeded. In accordance with one embodiment of the invention, the dynamic PON device accepts M wavelengths on a single optical fiber. The output of the dynamic PON device includes N output ports. Each of the M signals can be delivered to none, some or all of the N output ports. At its input, the DPON includes an optical amplifier for amplifying the multi-wavelength input signal to a desired power level prior to splitting. A 1:N channel power splitter couples to the output of the optical amplifier. Each of the power splitter outputs contains all M wavelength channels of the optical fiber.

Abstract: A method and system for retrieving pages from a remote location. In one embodiment, pager users can access their pagers from a remote location, via a public switched telephone network, to retrieve messages (i.e. numeric, alphanumeric and voice messages) and/or perform any other pager operation by engaging in an interactive wireless dialogue with the pager via a public switched telephone network and the paging system, wherein the pager uses digital voice encoding techniques to provide verbal feedback to the remote user. The remote can dial the number of the individual pager from a remote location and enter a preprogrammed command sequence to initiate wireless dialogue with the pager. Once the wireless dialogue is initiated, the remote user can enter other pre-programmed commands to control the operation of the pager from the remote location (e.g. to retrieve messages sent to the pager). The pre-programmed commands can be part of a command set such as a DTMF command set.

Abstract: An optical transceiver that is particularly adapted for free-space optical telecommunication uses the same optical path for received and transmitted light to a large extent to avoid duplication of optical elements. Received light is split so that different portions can be sent to physically spaced photodetectors, one of which is for detecting optically received information, and others of which are for detecting misalignment of the transceiver. In this way, the alignment detectors do not interfere with light reception by the information detector.

Abstract: Free-space optical transmission of analog information is facilitated by transmitting constant-amplitude pilot information with the other information. The amount of attenuation of the pilot information at the receiver is detected and used to control the amount by which received information is amplified. In this way the deleterious effects of free-space optical attenuation are substantially eliminated. The pilot information may be transmitted either via its own separate light frequency or wavelength, or as a distinguishable part of a larger quantity of information that is used to modulate one light frequency or wavelength.

Abstract: A free-space wavelength division multiplexing system is provided having a demultiplexer and receiver arrangement. The demultiplexer and receiver arrangement may be based on a rotatable interference filter. A desired wavelength can be selected by adjusting the angle of the interference filter with respect to the incoming light beam. Alternatively, the demultiplexer and receiver arrangement may be based on a diffraction grating. Multiple wavelengths of light are diffracted at different angles, which spatially separates each wavelength in the system. A corresponding multiple-element linear photodetector array is used to receive the spatially separated optical signals.

Abstract: An optical transmitter is provided for use in a free-space optical communications system. The transmitter has a laser source with a tunable wavelength and adjustable power. A beam splitter divides the output beam from the laser source. A first portion of the divided beam is transmitted to a remote receiver through the atmosphere. A second portion of the divided beam is passed through a local optical path to a local receiver. The local optical path may be either a portion of the atmosphere local to the transmitter or may be an atmospheric spectral attenuation simulator. Processing circuitry receives signals from the local receiver that indicate the amount of attenuation of the second portion of the beam in the local optical path. The processing circuitry may adjust the wavelength and power output of the laser source to optimize transmission of the first portion of the beam to the receiver based on the amount of the attenuation measured in the local optical path.

Abstract: Methods and apparatus for providing a secure optical communications link are disclosed. Communications information is encrypted with a security key. An optical beam is then modulated with both the security key and the encrypted communications information, with different modulation schemes being used for each. The dual-modulated optical beam is then transmitted to a receiver. At the receiver, the optical beam is split into first and second optical beams. First and second demodulators are then employed to demodulate the optical beams to recover the encrypted communications information and its data rate, and the security key and its data rate. The encrypted communications information, the security key, and the data rate information are then sent to decryption and timing circuitry which decrypts the encrypted communications information to obtain the original unencrypted communications information.

Abstract: The cells of a wireless communications system can be subdivided into smaller subcells, in each of which the available radio frequencies can be re-used to allow denser use of the system. To avoid having to run hard-wired communications links to broadcast antennas of the subcells, substantially unguided, free-space, optical communication is used between the antenna that formerly served the cell and the subcell antennas. The existing hard-wired connection from the central antenna to the remainder of the wireless communications system infrastructure continues to be used for communication to and from the cell.

Abstract: A system is provided for tracking a free-space optical communications beam. The incoming beam is split by a beam splitter. One portion of the incoming beam is focused onto a high-speed photodetector. Another portion of the incoming beam is passed through a target pattern optical element. A resulting target pattern is formed on a two-dimensional active pixel sensor array. The alignment of the system can be adjusted based on the position of the target pattern on the sensor array.