Control arrangement for optical mechanical switches

Details Control arrangement for optical mechanical switches Control arrangement for optical mechanical switches

2000-03-02

2001-10-09

Sanghavi, Hemang (Department: 2874)

Optical waveguides

With optical coupler

Switch

C385S017000, C385S018000, C385S019000, C385S024000, C359S199200

Reexamination Certificate

active

06301402

ABSTRACT:

TECHNICAL FIELD
This invention relates generally to the field of optical switching and in particular to arrangements and methods for monitoring and control of optical mechanical switches and switching systems.
BACKGROUND OF THE INVENTION
Optical mechanical switches such as microelectromechanical switching devices have become increasingly used for applications for which no comparable non-mechanical electronic device is available. Even for switching applications for optical communication, telemetry, and information processing systems, for which non-mechanical electronic switching devices do exist, a need for augmented capabilities is frequently met by optical mechanical switching devices.
For both microelectromechanical switches (MEMS) and other optical mechanical switches, a need exists for monitoring and improving their performance. At present this need typically is addressed by monitoring a customer's signals traveling through the system. Since a customer's signals frequently have a very large dynamic range, this technique requires the use of detectors with a dynamic range at least as large. A further drawback is that this technique requires a customer's signals to be present. Such signals are available only after a cross-connect has been provided. If the service provider chooses to modulate the customer's signals to ease design of the detection circuit, other problems, such as noise, result. Even the DC signals used by some providers are susceptible to, and may cause, noise.
Accordingly, improved monitoring techniques are urgently needed.
SUMMARY OF THE INVENTION
According to the invention, the performance of an optical mechanical switch is monitored independently of the presence of any customer signal.
According to a feature of the invention, a modulated optical signal is generated at a wavelength that is out-of-band with respect to the wavelengths of any transmission signals that may appear. The modulated optical signal is directed toward the optical mechanical switch, and system control parameters are changed to maximize a detected signal at the output of the optical mechanical switch.
Advantageously, any remnants of the modulated optical signal may be removed before arriving at any customer-related terminal. Optical cross-connect switching circuits are exemplary circuits in which the invention may be applied.
According to a preferred implementation of the invention, the modulated optical signal is inserted before or during the transmission of any customer signal. If accomplished before the transmission of any customer signals, the relevant switch control parameter is dithered in order to maximize the amplitude of the detected signal. During the transmission of customer signals, a less obtrusive change of a switch control parameter is employed. In either case, the detected signal is used in a servo system to reduce system loss. The preferred implementation includes a rotatable mirror as component, or central operator, on an optical mechanical switch fabric.
Further advantageously, since input monitoring and control signals are at known levels, the needed dynamic range for the detector is much reduced.
According to a further aspect of the invention, a method for monitoring and controlling an optical mechanical switch includes the steps of generating a modulated optical signal at a wavelength that is out-of-band with respect to the wavelengths of transmission signals that may pass through the optical mechanical switch, routing the modulated optical signal toward the optical mechanical switch to be rerouted by the optical mechanical switch toward an output port, detecting at the output port a modulation signal of the modulated optical signal, and changing a property of the optical mechanical switch to increase an amplitude of the detected modulation signal.
Further features and advantages of the invention will become apparent from the following description.


REFERENCES:
patent: 6205267 (2001-03-01), Aksyuk et al.
patent: 6222954 (2001-04-01), Riza

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