A computer-controlled optical amplifying apparatus, which includes an optical amplifying unit including an optical amplifying medium and an optical amplifying control unit controlling the optical amplifying unit under the control of a computer. This optical amplifying control unit is constituted by a status monitoring unit for monitoring the status, an optical output control unit for controlling the optical amplifying unit in accordance with the result of monitoring of status; and a status restoring unit for initializing the control status of the optical output control unit by initializing the computer when detecting an occurrence of the abnormal status by the result of monitoring of status and restoring the optical output control unit to the control status before occurrence of the related abnormal status within a relaxation time inherent in the optical amplifying medium occurring accompanied with this initialization.

Optical amplifying apparatus

The present invention teaches a novel technique for properly aligning the various channel positions of an optical signal splitter/combiner device, such as a DWDM, and associated optical transmitter(s), often a laser. In particular, the described technique establishes and utilizes feedback links between the operating temperature of the splitter/combiner and the operating temperature or operating current of the transmitter(s) to accurately manipulate the wavelengths of these devices in a manner that results in accurate alignment of the device wavelengths to the desired grid of channel positions, λ0, λ1, λ2, λ3, . . . , λn. Furthermore, by providing this active alignment or tracking scheme, the techniques of the present invention allows optical systems to more effectively operate at smaller channel spacings, i.e. ≦ about 50 GHz between adjacent channel positions, and with larger number of channels per device, i.e. ≧ about 32 channels.

Method and apparatus for wavelength-channel tracking and alignment within an optical communications system

A laser diode driver with automatic power control in which start-up characteristics are controlled to avoid unsafe power levels at a driven laser is disclosed. The laser diode driver according to the invention produces a bias control signal that controls a bias current source such that the bias current supplied to the laser is maintained below a predetermined level during a start-up period.

Laser diode driver having automatic power control with smooth enable function

In-flight entertainment systems provide entertainment for passengers on commercial airline flights. Presently, usually on longer flights, video entertainment is commonly available on in-flight passenger entertainment systems. In-flight entertainment systems can display video on a variety of display monitors ranging from a conventional CRT display to a more modern Liquid Crystal Display (LCD). Generally most displays are connected to the aircraft electronic system via a ARINC 722 connector. The ARINC 722 connector commonly provides an electrical interface between the aircraft and the video system, whether the video system is a CRT or LCD type monitor. With the increasing use of LCD monitors there is a greater need for the ability of the display monitor to be able to report its status. The need for status reporting is increased because the LCD monitors are often greater in number than the prior art CRT monitors and because malfunctions are less obvious. Several methods for providing status information from video displays have been proposed. Embodiments of the present invention comprise a system in which data can be requested by repeating commands, such as turn on, a number of times within a predetermined time interval. Because embodiments of the invention use an existing command, which can be the repeated without affecting the functioning of legacy systems, the need for modification of the airline and monitor systems is greatly reduced.

Data request method without using dedicated connections

A method embodiment of the invention includes a scheme for trimming and compensation of a laser emitter in a fiber optic link A laser emitter is provided Also a reference optical power value is determined using data models of laser emitter performance generated by statistical analysis of sample population of lasers that are similar to the subject laser emitter The performance of the subject laser is measured and qualified optical power levels for the subject laser emitter are determined using the reference operating power value and measured performance of the subject laser emitter The driving current of the subject laser emitter is adjusted to compensate for changes in temperature until the optical power of the subject laser emitter obtains a desired qualified optical power level Related methods of determining qualified optical power levels for a laser emitter in a fiber optic link are also disclosed As are methods of determining a reference optical power value for a laser emitter to be coupled in a fiber optic link Fiber optic links capable of trimming and compensation in open and closed loop configurations are also disclosed

Laser trim and compensation methodology for passively aligning optical transmitter

An optical modulating and amplifying apparatus includes an optical amplifier and a modulator. In the apparatus, an input optical signal and an excited light are combined with each other to produce an output light signal. The excited light from a laser diode is sensed by a photodiode. The sense signal includes a bias and an amplitude to be respectively detected by a mean value sensor and a modulation signal sensor. A modulation degree of the excited light is computed by a divider. A control signal to develop a predetermined modulation degree is delivered from a control signal generator to a variable gain amplifier. In response to the control signal, the amplifier controls the amplitude of the oscillation signal from an oscillator. A laser diode driver adds a bias to the oscillation signal to drive the laser diode. The modulation degree is kept unchanged regardless of variation in an output level of the excited light so as to achieve the modulation with a high signal-to-noise ratio.

Optical modulating and amplifying apparatus capable of achieving modulation with high signal-to-noise ratio

A reproducing circuit is disclosed having a photo-diode for extracting a signal component of a monitor signal from an electric signal converted from an optical signal using a band pass filter 108 and an envelope detector circuit 111. The output of the photo-diode 106 is smoothed by a capacitor 12 via a buffer amplifier 11. A threshold voltage control circuit 13 converts the smoothed signal voltage with a predetermined ratio to produce a threshold voltage. A discriminator 115 converts the extracted monitor signal component into a binary signal using the threshold voltage as a reference. Since the smoothed voltage varies in accordance with the average intensity of optical signal, the monitor signal can be appropriately converted into a binary signal in accordance with the intensity of optical signal. Further, since the smoothing is performed by a capacitor, the circuit structure can be simplified.

Reproducing circuit of monitor signal

It is the object of the invention to provide a wavelength stability circuit used in a WDM optical transmission system, in which the spacing of wavelengths between adjacent optical signals are always so controlled as to keep a prescribed value. The two optical signals with different wavelengths are respectively generated by two laser diodes and multiplexed by an optical coupler. A portion of the multiplexed optical signals is supplied to an optical heterodyne detection circuit, where the spacing of the wavelengths between the two optical signals is detected. The spacing of the wavelengths between the optical signals is converted into an electrical signal by an O/E converter and a frequency counter, and the electrical signal is compared with a standard voltage in a comparator. The spacing of the wavelengths between the two optical signals is always controlled and stabilized by a control circuit and keeps a prescribed value, where the lasing wavelength of one of the two laser diodes is controlled in accordance with the result of comparison of the comparator.

Wavelength stability circuit

A submarine optical gain equalizer installed on a submarine optical transmission cable 5 . The submarine optical gain equalizer comprises a pressure housing 1 , in which an optical gain equalizer and n through-fibers are installed. Input and output ports of the optical gain equalizer and the through-fibers are formed in the outside of the pressure housing. The submarine optical gain equalizer equalizes levels of signal light having wavelengths different each other caused by optical fiber amplifiers. In general, one submarine optical gain equalizer is installed for 40 optical fiber amplifiers on a submarine optical cable.

Submarine optical gain equalizer, submarine optical transmission line and its installation method

PROBLEM TO BE SOLVED: To use an inexpensive OTDR measurement device and to improve the measurement accuracy of fault point evaluation by providing a branch port on a branch line branched from a transmission line. SOLUTION: In the case that a fault point is present between a terminal station A and this remote excited repeater 20, a normal OTDR measurement device 28 is connected to the branch port 251 close to the fault point. Optical signals are originated from the OTDR measurement device 28 through the branch port 251 and made to pass through an optical demultiplexer 23 and the transmission line 21 and the optical signals are sent through a transmission port 221 to the fault point. Thereafter, by receiving and inspecting the reflected light and scattered light of the optical signals from the fault point in the OTDR measurement device 28, the position of the fault point is evaluated. By such constitution, by providing the branching ports 251 and 252 which are access ports for the OTDR measurement device on the outside of the remote excitation repeater 20, the fault point position is evaluated by the OTDR measurement device 28 from the middle of a non-relay system and fault point evaluation is easily executed.

Hiroshi Sakuyama

Papers

Optical modulating and amplifying apparatus capable of achieving modulation with high signal-to-noise ratio

Reproducing circuit of monitor signal

Wavelength stability circuit

Submarine optical gain equalizer, submarine optical transmission line and its installation method

Remote excited repeater and remote excited relay method