Free-space optical communication system

A free-space communication system and method of operation includes a first communication device physically coupled to a substrate and having an optical transmitter for communicating information. A second communication device is physically coupled to the substrate and has an optical receiver for communicating information. An adjustable optical beam deflector is physically coupled to the substrate for optically coupling the first communication device and the second communication device via an optical beam including a free-space optical portion. A feedback system includes a non-optical communication link for receiving information regarding the optical beam. The feedback system controls the adjustable optical beam deflector to direct the optical beam to improve the quality of an optical link incorporating the optical beam. At least one sensor is physically coupled to the substrate for monitoring one or more environmental conditions and providing information of the one or more environmental conditions to the feedback system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to information systems and more specifically to a free-space optical system in an information system.

2. Description of the Related Art

Information systems such as computer systems, cellular phones, wireless devices, PDA's, and electronic control systems for automobiles utilize multiple integrated circuit chips for performing functions of the system. These integrated circuit chips are communicatively coupled via wired busses e.g. wires or circuit traces for exchanging information.

Recently, systems have been proposed where information may be exchanged between devices of an information system with optical communication for increasing bandwidth and speed. One solution is to use wave guides for carrying the optical signals between chips. One example is the use of wave guides to exchange information between a processor and a memory.

One problem with the use of a waveguide is that it may be difficult to align components to a wave guide on a circuit board. Another problem is that the waveguides themselves add expense to the system.

Information may be transferred optically where at least some portion of the optical link passes through free-space (i.e. not through a wave guide). These systems may be referred to free-space optical systems in that at least some portion of the link passes through free-space. An optical link passing through “free-space” includes not only an optical link passing through atmospheric air, but also includes an optical link passing through any gas, vacuum, or liquid where the container of such medium does not act as a waveguide.

One problem with a free-space optical system is that the components of the link must be aligned within certain tolerances to meet information transmission requirements. For example, the optical transmitter, deflector structures, and the optical receiver must be aligned to ensure a desired level of information transmission.

Although care can be taken to ensure that the components are aligned when assembled, such systems may be subjected to vibration (e.g. dropping) or temperature variation during use. For example, components of an optical link may become misaligned if a cell phone or notebook computer is accidentally dropped on a surface. Furthermore, the cost for designing and assembling components that are precisely aligned may be cost prohibited.

What is needed is an improved system for a free-space optical communication system.

DETAILED DESCRIPTION

FIG. 1is a block diagram of a free-space optical communication system according to one embodiment of the present invention. System101includes an adjustable beam deflector unit (ABDU)112for adjusting a deflection of an optical beam of a free-space optical communication system. The adjustments to the ABDU are made by a feedback system using information provided over a non optical communication link. Accordingly, if system101is subjected to an excessive vibration or temperature variation or if the components of the free-space optical system become misaligned for other reasons, system101may readjust the defection of the optical beam to correct for any misalignment due to these reasons.

System101includes a number of communication devices (e.g. processor103, memory107, and peripheral105) that communicate with each other via optical beams. For example, in the embodiment ofFIG. 1, processor103provides information to memory107via an optical beam including free-space optical beam portions111and121and receives information from memory107via an optical beam including free-space optical beam portions119and113. Processor103provides information to peripheral105via an optical beam including free-space optical beam portions111and117and receives information from peripheral105via an optical beam including free-space optical portions113and115. An optical beam is a beam of radiation having wavelengths in the optical range (e.g. signals with wavelengths in the range of approximately 200-2000 nm).

In one embodiment, processor103is the system processor for controlling system101. Peripheral105maybe any one of a number of peripheral devices, (e.g. keyboard controller, mouse controller, external network controller, external wireless transceiver, CD drive controller, DVD drive controller, a hard drive controller, or a socket mounted device). Memory107may be the main operating memory for system101and may include one or more chips (e.g. as in a DRAM or SRAM type memory) or it may be a non volatile memory (e.g. flash or hard drive memory). Other systems may include a greater number of communication devices (e.g. more memories, additional processors, and other peripherals) that communicate by optical beams that include free-space optical beam portions.

In the embodiment shown, each communication device includes an optical transmitter (OT) and an optical receiver (OR). Processor103includes OT123and OR125, peripheral105includes OT129and OR131, and memory107includes OT137and OR139. Information is provided to the optical transmitters to generate an optical beam with the information encoded therein. The optical transmitters include circuitry for converting information from one form (e.g. electrical signals) and devices (e.g. a laser) for generating an optical beam that includes the information. In one embodiment, the OT and processing circuitry of processor103are located on the same integrated circuit die. See for example the application entitled “Optical Communication Integration,” having a common assignee, having inventors Perry H. Pelley and Dennis C. Hartman, and having the same filing date, all of which is hereby incorporated by reference in its entirety.

Each optical receiver includes devices (e.g. a photodiode) for receiving the optical beam and converting the information into another form (e.g. electrical signals) to be used by the receiving device.

The free-space optical beam portions shown inFIG. 1represent optical beams of one or more optical frequencies. In some embodiments, each frequency may comprise an independent data stream which may be separated out by an optical receiver or which may be directed to a different communication device via ABDU112. In some embodiments, each beam portion may comprise multiple parallel beams, each of which may have multiple frequencies in some embodiments. For example, beam portion111may include 8 parallel beams for implementing a parallel optical bus. InFIG. 1, the beam portions are shown as unidirectional. However, a beam portion may be implemented where the corresponding beam portion in the opposite direction (e.g. portions111and113) is in the same physical space but at different frequencies.

With a free-space optical communication system, it is important for the free-space optical beam to strike the sensing circuitry (e.g. photodiode) at a targeted location. The closer the beam is to the targeted location, the better the performance of the communication link (e.g. the greater the signal-to-noise ratio). Misalignment of a beam may occur in some embodiments due to excessive vibration where components of system101may become partially dislodged or moved due to the vibration. Also, a sudden change in temperature may result in a movement of components with respect to each other. For example, where the communication devices are physically coupled to a substrate (e.g. circuit board201), a change in temperature may cause the substrate to bow where the communications devices move with respect to each other.

System101includes a feedback system for obtaining information from a communication device receiving an optical beam and adjusting the adjustable beam deflector unit112to direct the beam to the targeted location of an optical receiver to improve the quality of the optical link if the components become misaligned. In one embodiment, the feedback may be used to increase or decrease beam intensity to minimize power while maintaining signal-to-noise ratio.

In the embodiment shown, the feedback system includes a non optical communications link151that is communicatively coupled to each communication device and a controller114communicatively coupled to control ABDU112for directing the optical beams. In one embodiment, processor103is part of the feedback system. In such embodiments, processor103receives information regarding the reception of an optical beam from the controllers133and141of peripheral105and memory107via link151and calculates appropriate adjustments needed to ADBU112. Processor103provides those adjustments to controller114to adjust ADBU112to direct the optical beams with respect to the optical receivers (131,139, and125) for improved information transmission. Processor103uses the information from its own OR125to adjust ABDU112for directing free-space optical beams hitting OR125.

In one embodiment, the feedback system receives information from the receiving device that is indicative of the accuracy of an optical beam striking the desired target of the optical receiver. For example, in one embodiment, the feedback system receives optical signal intensity information, which is an indication of the intensity of the received optical beam at a receiver. The greater the intensity, the closer the beam is centered on its desired target. In other embodiments, the feedback system may receive information regarding the signal-to-noise ratio of the information received by the receiving communication device. In other embodiments, the optical receiver may also include a number of diodes surrounding the target diode. The surrounding diodes would used to detect if the beam is offset from the target diode. Such information would be used for adjustment of the beam or for cancellation of feed through from adjacent beams.

In other embodiments of a feedback system, controller114may include logic or a processor that receives the information from the communication devices (including processor103) via link151and calculates the adjustments needed for ABDU112. In one embodiment, processor103(or controller114if it includes a processor) executes a software program for adjusting ABDU112. In other embodiments, such adjustments may be made by firmware or hardware.

System101also includes a number of sensors for sensing environmental conditions of system101. Processor103, peripheral105, memory107, and ABDU112each include sensors127,135,143, and154respectively. These sensors maybe temperature or vibration sensors (e.g. accelerometers) for sensing temperature and vibrations. System101also includes temperature sensor149and accelerometer147. Processor103uses the information from these sensors for adjusting ABDU112and for anticipating future changes.

In one embodiment, communications link151is a serial, wired link. In other embodiments, linked151may be implemented as a wired parallel bus. In one embodiment, link151may be implemented as an RF communication system (e.g. Ultra Wideband (UWB)). In the embodiment shown, all communication devices, controller114, sensor149, and accelerometer147are communicatively coupled to link151. However, in other embodiments, the different devices may be communicatively coupled by various links. For example, processor103may be communicatively coupled by a different link to controller114. In one embodiment, link151operates at a considerably lower data rate than those of the optical links of system101.

Providing a free-space optical system with a feedback system that uses non optical feedback may advantageously provide the system with a way to adjust the optical beams even when factors such a sharp vibration would cause a misalignment that completely cuts off the optical connection. For example, if system101were dropped on the floor and the components were to become misaligned, the feedback system could be used to adjust ABDU112to direct the beam such that it strikes a desired target. Furthermore, using the non optical link for feedback frees up bandwidth for the transfer of information over the optical link. If the optical links were used for feedback, then the controllers of the communication devices would have to be configured to add overhead information (or additional over head information) to the optical link.

FIG. 2shows a perspective view of one embodiment of a physical implementation of system101. In the embodiment ofFIG. 2, system101is implemented on a substrate (circuit board201), wherein various components of system101are implemented in integrated circuit package chips (chips) physically coupled to circuit board201. InFIG. 2, processor103is implemented in chip203and chip204mounted to board201. The optical transmitter123and optical receiver125of processor103are implemented in transceiver chip204connected via a wired connection (e.g. circuit traces) to chip203. Link151is implemented as circuit traces257. Memory107and peripheral105are implemented on plug-in cards205and207. Cards205and207include various chips mounted on the cards for implementing the components of those devices. In the embodiment shown, the optical transmitters and optical receivers of memory107and peripheral105are implemented in transceiver chips223and221, respectively. The circuitry of cards205and207are physically coupled to circuit board201in that cards205and207are inserted into sockets209and211, respectively, which are mounted to board201.

Sensor149and accelerometer147are each implemented as chips mounted to board201. Controller114is implemented in chip214. ADBU112is mounted to board201.

In the embodiment shown, an optical link from transceiver chip204to transceiver chip221includes a free-space optical beam portion261and a free-space optical beam portion265where ADBU reflects the path of beam portion261to the path of beam portion265to target the receiving circuitry of transceiver chip221. The optical beam between chips221and204includes free-space optical beam portion265directed through ADBU112to the path of free-space optical beam portion261. ADBU112also directs beam portion261to the receiver circuitry of chip223via the path of free-space optical beam portion263. Likewise, the optical beam between chips221and204includes the path of free-space optical beam portion265directed through ADBU112to the path of free-space optical beam portion261.

The embodiment ofFIG. 2includes two additional communication devices. One communication device is implemented in chip219and transceiver chip218, both mounted to board201. The second device is mounted to card270inserted in socket222. Card270includes a transceiver chip (not shown). In one embodiment, card270may implement another memory circuit and chips218and219may implement a peripheral such as a hard drive controller or graphics accelerator.

In the embodiment shown, ABDU112reflects the optical beams between transceiver chip204and transceiver chips218,221, and223. For example, ABDU112reflects optical beam portion261to optical beam portion265to strike transceiver chip221. However, the optical beam from chip204(portion261) deflects as it passes though ABDU112to card270(beam portion271).

In the embodiment ofFIG. 2, the optical beams are shown as two way beams, however, in other embodiments, the beams may be one way. In some embodiments, not all components are optically coupled. For example, a system using optical links might also include a keyboard controller using a conventional wired interface or a hard drive controller using an RF interface.

Also other embodiments may include optical beams between other communication devices of system101. For example, system101may allow for an optical beam generated by transceiver chip221to pass through ABDU112to card270, thus allowing direct communication, e.g. between a peripheral and a memory without intermediation of processor103.

In other embodiments, system101may include more than one ABDU. In some embodiments, the optical beams may be deflected by more than one beam deflection unit. In one embodiment, a beam may also be deflected by a fixed beam deflecting unit.

ABDU112includes structures for directing an optical beam. In some embodiments, ABDU112includes structures that are reflective (e.g. such as mirrored surfaces). In other embodiments, ABDU112includes structures that are transmissive where a beam passes through the structure and is directed in the structure. In some embodiments, the ABDU112may include both reflective and transmissive structures

FIG. 3is a diagram of one embodiment of an ABDU according to one embodiment of the present invention. ABDU301includes a structure303having a number of movable mirrored surfaces305309,313, and317that are movable by micro-electro mechanical system (MEMS) devices307,311,315, and319, respectively. In one embodiment, each mirrored surface is moved to a desired position of reflection by applying a particular voltage or current to its associated MEMS device. In one embodiment, the controlling voltage is generated by a controller (e.g.112) in response to corrective adjustment information. By moving the mirror surface with a MEMS device, the location of the mirror can be controlled electronically by the feedback system to direct an outgoing beam portion to a desired target by adjusting the angle of reflection. InFIG. 3, incoming beam portion321strikes mirrored surfaces305and309and is reflected as beam portion323to a desired target. Also, incoming beam portion321is also directed by mirrored surfaces313and317and is reflected as beam portion327to a second desired target. Providing an ABDU with multiple mirror surfaced controlled by MEMS devices provides an ABDU that can “split” an incoming beam into multiple beams to different targets, where each of those beams can be individually directed to a desired target.

In one embodiment, the mirrored surfaces are metal films on independently-controlled MEMS devices. In one embodiment, the MEMS device includes two structures (not shown) that are movable with respect to each other by applying a current or voltage to each structure. In one embodiment, the MEMS structures are made of silicon. The mirrored surface is attached to one structure, and the other structure is fixably coupled to board201. An optical beam can be directed during operation by moving the structures of the MEMS device with respect to each other. In other embodiments, a MEMS device may have other structures and/or work in other ways.

FIG. 4is an other embodiment of an ABDU. ABDU401includes a liquid crystal beam deflector402with a liquid crystal layer409between glass layers407and405. Liquid crystal layer409includes liquid crystal molecules that, when subject to an electric field, rotate to a degree dependent upon the strength of the electric field. Optical radiation passing through these rotated molecules are defected at an angle depending on the rotation of the molecules. The angle at which optical energy is deflected is dependent upon the strength of the electric field. The electric field at a particular location of layer409is controlled e.g. by the intensity of a pulse applied by controller403at that location. With some embodiments, light is deflected by different degrees at different locations of layer409, depending upon the intensity of the signal at that location. Conversely, incoming beam portion421can be directed to different targets (e.g. as beam portions423,425, and427) depending upon the strength of the electric field at the locations of layer409in which beam portion421enters. ABDU401is transmissive in that optical radiation passes through deflector402. In other embodiments, a liquid crystal layer may have other structures and/or work in other ways.

FIG. 5is an ABDU according to another embodiment of the present invention. ABDU501includes a liquid crystal deflector502with a liquid crystal layer509located between glass layers507and505. A reflective surface508is located on the back side of layer505. An incoming beam portion521is directed by passing through layer509according to a field generated by controller503. After passing through layer509, the optical beam is reflected back through layer509(where it can be further directed by layer509) as out going beam portions529and527. In this embodiment, ABDU501is a reflective ABDU. In some embodiments, mirrored surface508may be separated from glass layer505. In some embodiments, mirrored surface508may be located sufficiently away from layer505such that an optical beam is not re-reflected back through liquid crystal layer509.

FIG. 6is an ABDU according to another embodiment of the present invention. ABDU601includes both transmissive and reflective portions. ABDU601includes a liquid crystal defector604that includes liquid crystal layer609between glass layer605and607. ABDU601includes mirrored surface611whose position is controlled by a MEMS device. An coming beam portion621is directed by liquid crystal layer609. A portion of beam portion621is passed through layer609and is directed out as beam portion613where the beam is deflected in layer609. A second portion of beam621is directed by layer609and then reflected back by mirrored surface611through to layer609where it can be further directed as optical beam portion617. With the embodiment ofFIG. 6, ABDU601can direct a beam through ABDU in one direction and reflect the beam back in a second direction. Accordingly an incoming beam can be directed to receivers on both sides of ABDU601.

Also with the embodiment of601, a beam portion617can be directed by controlling liquid crystal beam deflector layer609and further by moving mirrored surface611by controlling the MEMS device. In the embodiment ofFIG. 6, both liquid crystal beam deflector layer609and mirrored surface611are controlled by controller603. Accordingly, the range adjustment of beam portion617can be increased with the use of both liquid crystal and MEMS controlled beam deflection devices.

FIG. 7sets for one embodiment for adjusting an ADBU to direct optical beams for realignment during operation of an optical system (e.g. system101).

In operation701, the optical links of an optical system are initialized where optical beams are transmitted to transfer information between communication devices of system101.

In operation703, the feedback system obtains transmission quality metric information (e.g. optical signal intensity, signal-to-noise ratio information) from the communication devices over non optical link151. The feedback system also obtains temperature and vibration information as well. In one embodiment, this information may be obtained by processor103polling each device on link151. However, this information may be obtained by other ways in other embodiments.

In operation704, correction information is calculated (e.g. by processor103in one embodiment). The correction information is calculated using the metric information and also sensor information in some embodiments. In705, the correction information is sent to controller114to adjust ABDU112for directing any optical beams of an optical link that are below a transmission quality threshold. In some embodiments, operation704may comprise predicting future changes in optical quality metrics.

In707, the feedback circuitry waits a period of time for ABDU112to be adjusted and then transitions back to operation703where it obtains metric information from the receiving devices again. Accordingly, the feedback system can evaluate the adjustments made in operation705and make further adjustments in a subsequent instantiation of operation705. In the embodiment shown, the feedback system is continually gathering quality metric information and adjusting ADBU112to ensure that the optical links of system101are operating above a desired threshold.

With the system ofFIG. 7, optical beams are continually monitored and directed if necessary to account for changes in relation among the optical transmitter, optical receiver, and deflector units. Such changes may be due e.g. to vibration or changes in temperature. Consequently, if the system is dropped or damaged, the system may still continue to be operable in that the ABDU can be controlled to realign the optical communication links.

Also, in some embodiments, the amount of direction of an optical beam may vary depending on temperature. For example, the deflection characteristics of a liquid crystal layer may vary with temperature. Accordingly, the feedback system of system101may be used to compensate for such variation in temperature.

In some embodiments, the feedback system uses the temperature and/or vibration sensor measurements for making corrections for ABDU adjustment. In one embodiment, the extent that the ABDU is moved is based on the amount of vibration or variation in temperature. For example, if the amount of vibration is great (e.g. with a drop of system101), an optical link may become non aligned by a great margin. Accordingly, the feedback system may significantly alter the position of the ABDU such that the beam may more quickly meet the quality threshold. However, if the amount of vibration or temperature variation is not great, then only a minor amount of adjustment is made.

In some embodiments, the measured vibration and/or temperature may be used to estimate the location that a beam needs to be directed for improved transmission quality.

For example, if the ABDU includes a liquid crystal beam deflector layer (e.g.409) whose amount of direction is dependent upon temperature, then the feedback system may use the temperature information for adjusting the direction of the liquid crystal layer to compensate for the temperature variation. In some embodiments, the ADBU may include a temperature sensor (e.g. sensor154) for measuring its temperature. Also, if the amount and direction of substrate warping is dependent upon temperature, then the feedback system may use the temperature information for adjusting the ADBU to compensate for the warping.

In some embodiments, the vibration information may include direction information that indicates the direction of vibration. The feedback system may use this direction information for determining the amount and direction of optical beam directing by the ABDU. For example, if system101is dropped in a certain direction, this information may be used to adjust a beam in a certain direction with respect to an optical receiver.

In some embodiments, the feedback system may have memory that allows it to store previous beam directing information with respect to previous measurements of temperature and/or vibration. For example, the feedback system may store a previous ABDU setting with respect to a temperature range that provided the optical link with a sufficient transmission quality. As another example, the memory of the feedback system would store previous adjustment information in regards to specific vibration amplitude and/or direction. The storage of such information may be used to provide for more accurate correction information for adjusting the ABDU. With more accurate information, an optical link may be more quickly brought back into compliance from an alignment altering event.

Although an optical system has been described in regard to its components physically coupled to a circuit board substrate, an optical system with an ABDU and feedback system may be implemented in an optical system where the components are physically coupled to a package substrate. In such an embodiment, the components of the optical system may be encapsulated (either completely or partially) in encapsulant such that the entire optical system is on an integrated circuit chip package. In some embodiments, the package would have cavities for free-space optical beams. In some embodiments, a portion of the encapsulation would be transparent to optical beams.

In other embodiments, the ABDU may be used to direct an optical beam transmitted by one transmitter from one optical receiver of a first communication device to another optical receiver of a second communication device. For example, referring back toFIG. 2, in one embodiment, ADBU112may be controllable to direct a beam from transceiver chip204to either OTR chip221or OTR chip223depending upon whether processor103desires to communicate with peripheral105or memory107. With such embodiments, the ADBU and non optical feedback would provide an optical system flexibility in allowing a transceiver to communicate with any one of a number of devices without having to have the capability of communicating simultaneously with all.

In some embodiments, the feedback system may be utilized for shutting down an optical link if the feedback system determines that the link is permanently blocked. For example, if a component becomes loose during operation such that the feedback system can not direct a beam sufficiently to recover the link, the feedback system would be able to stop transmission of the beam and report an error. Stopping transmission of the beam would save energy. Also, if a beam becomes greatly misaligned, it may present a safety hazard. Further, an interruption of an optical beam may occur as part of an attempt to break into a system. Accordingly, the shut down feature may increase the security of the system.

In the embodiment shown, ABDU112is physically separate from the transceiver chip204. However, in other embodiments, ABDU112may be integrated with transceiver chip204. Also in some embodiments, ABDU112may be integrated with controller114. In some embodiments, the lens of an optical transmitter may be adjustable as well. Also in some embodiments, circuitry of chips203and204may be implemented in a single chip.

Also, in some embodiments, the system may include standard optical components such as a lens, a diffraction grating, a filter, a wave guide or other components.

In one embodiment, a system includes a first communication device physically coupled to a substrate and including an optical transmitter for communicating information. The system includes a second communication device physically coupled to the substrate and including an optical receiver for communicating information. The system also includes an adjustable optical beam deflector physically coupled to the substrate for optically coupling the first communication device and the second communication device via an optical beam including a free-space optical beam portion. The system further includes a feedback system including a non-optical communication link for receiving feedback information regarding the optical beam. The feedback system controls the adjustable optical beam deflector to direct the optical beam in response to the feedback information.

In another embodiment, a method includes communicating information from a first communication device physically coupled to a substrate to a second communication device physically coupled to the substrate by using an optical beam. The optical beam includes a free-space optical beam portion. The optical beam is deflected by an adjustable optical beam deflector physically coupled to the substrate. The method includes providing by the second communication device via a non-optical communication link, one or more quality metrics regarding a reception of the optical beam. The method also includes controlling the adjustable optical beam deflector to direct the optical beam in response to the one or more quality metrics.

In another embodiment, a system includes a processor physically coupled to a substrate and including an optical transceiver for communicating information. The system includes at least one device physically coupled to the substrate and including an optical transceiver for communicating information. The system also includes an adjustable optical beam deflector physically coupled to the substrate for optically coupling the processor and the at least one device via an optical beam including a free-space optical beam portion. The system further includes a feedback system physically coupled to the substrate and including a non optical communication link for receiving information regarding the optical beam. The feedback system controls the adjustable optical beam deflector to direct the optical beam.