Abstract: A non-volatile memory device includes an upper semiconductor layer including a first metal pad and vertically stacked on a lower semiconductor layer. The upper semiconductor layer includes a first memory group spaced apart from a second memory group in a first horizontal direction by a separation region, and the lower semiconductor layer includes a second metal and a bypass circuit underlying at least a portion of the separation region and configured to selectively connect a first bit line of the first memory group with a second bit line of the second memory group. The upper semiconductor layer is vertically connected to the lower semiconductor layer by the first metal pad and the second metal pad.

Abstract: A method of priming a minimum quantity lubrication (MQL) tool includes determining a category of the tool, supplying a short-prime MQL dosage if the tool is a first category or if both a second category and lubricated within a first predetermined timeframe, and supplying a long-prime MQL dosage if the tool is the second category and has not been lubricated within the predetermined timeframe. The category is based on internal passage complexity of the tool.

Abstract: A die-stacked memory device implements an integrated QoS manager to provide centralized QoS functionality in furtherance of one or more specified QoS objectives for the sharing of the memory resources by other components of the processing system. The die-stacked memory device includes a set of one or more stacked memory dies and one or more logic dies. The logic dies implement hardware logic for a memory controller and the QoS manager. The memory controller is coupleable to one or more devices external to the set of one or more stacked memory dies and operates to service memory access requests from the one or more external devices. The QoS manager comprises logic to perform operations in furtherance of one or more QoS objectives, which may be specified by a user, by an operating system, hypervisor, job management software, or other application being executed, or specified via hardcoded logic or firmware.

Abstract: A die-stacked memory device implements an integrated coherency manager to offload cache coherency protocol operations for the devices of a processing system. The die-stacked memory device includes a set of one or more stacked memory dies and a set of one or more logic dies. The one or more logic dies implement hardware logic providing a memory interface and the coherency manager. The memory interface operates to perform memory accesses in response to memory access requests from the coherency manager and the one or more external devices. The coherency manager comprises logic to perform coherency operations for shared data stored at the stacked memory dies. Due to the integration of the logic dies and the memory dies, the coherency manager can access shared data stored in the memory dies and perform related coherency operations with higher bandwidth and lower latency and power consumption compared to the external devices.

Abstract: A memory system includes a controller, a first memory module, and a second memory module. The first memory module includes a first number of memory packages and a second number of memory packages. The second memory module includes a third number of memory packages and a fourth number of memory packages. The first and third numbers of memory packages are selected to correspond to a same rank based on control signals from the controller. The control signals are transmitted from the controller to the first and second memory modules through respective ones of a plurality of optical channels.

Abstract: An integrated circuit and a manufacturing method thereof are provided. A chip size can be reduced by forming a memory device in which a ferroelectric capacitor region is laminated on a DRAM. The integrated circuit includes a cell array region having a capacitor, a peripheral circuit region, and a ferroelectric capacitor region being formed on an upper layer of the cell array region and the peripheral circuit region, and having a ferroelectric capacitor device.

Abstract: A memory chip package includes memory chips stacked, electrically connected one another, and configured to input and output an optical signal through an optical line formed by a via penetrating the memory chips. The memory chips input and output optical signals with different wavelengths, and each of the memory chips has an optical-electrical converter configured to convert an optical signal with a corresponding wavelength into an electrical signal and to convert an electrical signal into an optical signal with the corresponding wavelength.

Abstract: A memory module having a high data processing rate and high capacity is provided. The memory module may include a memory chip, a controller controlling an operation of the memory chip, an optical detector converting an external input signal into an internal input signal to transmit the converted signal to the controller, and an optical generator converting an internal output signal received from the controller into an external output signal. The optical detector converts an external input optical signal into an internal input signal to transmit the converted signal to the controller. The optical generator converts an internal output signal received from the controller into an external output optical signal.

Abstract: An optically controlled read only memory is disclosed. The optically controlled read only memory includes a substrate, a plurality of memory cells having optical sensors disposed on the substrate, and at least one shielding structure disposed on the optical sensor, in which the shielding structure selectively shields a portion of the optical sensor according to a predetermined layout. Preferably, the optically controlled read only memory of the present invention is capable of providing two types or more program codes and outputting different program codes carrying different function under different lighting condition.

Abstract: A monitoring system includes a serial advanced technology attachment dual-in-line memory module (SATA DIMM) with a circuit board, a motherboard having a monitoring unit, and a monitoring device. An edge connector is set on a bottom edge of the circuit board to engage in a memory slot of the motherboard. A SATA connector is arranged on the circuit board and connected to a storage device interface of the motherboard. The monitoring unit receives a working state signal and a data transfer rate signal of the SATA DIMM module and outputs the received signals to the monitoring device.

Abstract: A semiconductor integrated circuit capable of protection from card hacking, by which erroneous actions are actively induced by irradiation with light and protected secret information is illegitimately acquired, is to be provided. Photodetectors, configured by a standard logic process, hardly distinguishable from other circuits and consumes very little standby power, are mounted on a semiconductor integrated circuit, such as an IC card microcomputer. Each of the photodetectors, for instance, has a configuration in which a first state is held in a static latch by its initializing action and reversal to a second state takes place when semiconductor elements in a state of non-conduction, constituting the static latch of the first state, is irradiated with light. A plurality of photodetectors are arranged in a memory cell array. By incorporating the static latch type photodetector into the memory array, they can be arranged inconspicuously.

Abstract: Disclosed is a memory module which includes a memory chip; an external input/output terminal having an electrical signal input/output terminal and an optical signal input/output terminal; an optical signal processor configured to convert a first optical signal input through the optical signal input/output terminal into a first internal electrical signal and to convert a second internal electrical signal into a second optical signal; and a controller configured to provide a first data signal to the memory chip in response to a first external electrical signal input through the electrical signal input/output terminal or the first internal electrical signal and to transfer the second internal electrical signal to the optical signal processor or to output a second external electrical signal to the electrical signal input/output terminal in response to a second data signal output from the memory chip.

Abstract: A nanocrystal composite that includes a matrix including semiconductor nanocrystals, and a barrier layer disposed on at least a portion of the surface of the matrix and including a polymer with low oxygen permeability, low moisture permeability, or both.

Abstract: To include a superlattice laminate having laminated thereon a first crystal layer of which crystal lattice is a cubic crystal and in which positions of constituent atoms are reversibly replaced by application of energy, and a second crystal layer having a composition different from that of the first crystal layer, and an orientation layer that is an underlaying layer of the superlattice laminate and causes a laminated surface of the first crystal layer to be (111)-orientated. According to the present invention, the laminated surface of the first crystal layer can be (111)-orientated by using the orientation layer as an underlaying layer. In the first crystal layer of which laminated surface is (111)-orientated, a crystal structure reversibly changes when a relatively low energy is applied. Therefore, characteristics of a superlattice device having this crystal layer can be enhanced.

Abstract: Optically-coupled memory systems are disclosed. In one embodiment, a system memory includes a carrier substrate, and a controller attached to the carrier substrate and operable to transmit and receive optical signals, and first and second memory modules. The module substrate of the first memory module has an aperture formed therein, the aperture being operable to provide an optical path for optical signals between the controller and an optical transmitter/receiver unit of the second memory module.

Abstract: A memory module having a high data processing rate and high capacity is provided. The memory module may include a memory chip, a controller controlling an operation of the memory chip, an optical detector converting an external input signal into an internal input signal to transmit the converted signal to the controller, and an optical generator converting an internal output signal received from the controller into an external output signal. The optical detector converts an external input optical signal into an internal input signal to transmit the converted signal to the controller. The optical generator converts an internal output signal received from the controller into an external output optical signal.

Abstract: Disclosed are embodiments of a multi-chip assembly including optically coupled die. The multi-chip assembly may include two opposing substrates, and a number of die are mounted on each of the substrates. At least one die on one of the substrates is in optical communication with at least one opposing die on the other substrate. Other embodiments are described and claimed.

Abstract: A memory module having a high data processing rate and high capacity is provided. The memory module may include a memory chip, a controller controlling an operation of the memory chip, an optical detector converting an external input signal into an internal input signal to transmit the converted signal to the controller, and an optical generator converting an internal output signal received from the controller into an external output signal. The optical detector converts an external input optical signal into an internal input signal to transmit the converted signal to the controller. The optical generator converts an internal output signal received from the controller into an external output optical signal.

Abstract: A heterostructure of multiferroics or magnetoelectrics (ME) was disclosed. The film has both ferromagnetic and ferroelectric properties, as well as magneto-optic (MO) and electro-optic (EO) properties. Oxide buffer layers were employed to allow grown a cracking-free heterostructure a solution coating method.

Abstract: The memory module includes a plurality of memory devices, a first connector and a second connector. The first connector is disposed at a first position on the memory module. The first connector is configured to carry low-speed signals for the memory devices. The second connector is disposed at a second position on the memory module, different from the first position. The second connector is configured to carry high-speed signals for at least one of the memory devices. The high-speed signals are a higher speed form of signaling than the low-speed signals. The memory system may include at least one slot electrically connected to a chip set and at least one memory module electrically connected to the slot via the first connector. A transmission line such as a fiber optic cable electrically connects the second connector and the chip set.

Abstract: Examples of a computer system packaged in a three-dimensional stack of dies are described. The package includes an electrical die and an optical die coupled to and stacked with the electrical die. The electrical die includes circuitry to process and communicate electrical signals, and the optical die includes structures to transport optical signals. The electrical die has a smaller area than the optical die so that the optical die includes an exposed mezzanine which is configured with optical input/output ports. Additionally, the packaging can be configured to provide structural support against insertion forces for external optical connections.

Abstract: Various embodiments of the present invention are directed to stacked memory modules. In one embodiment of the present invention, a memory module comprises at least one memory-controller layer stacked with at least one memory layer. Fine pitched through vias (e.g., through silicon vias) extend approximately perpendicular to a surface of the at least one memory controller through the stack providing electronic communication between the at least one memory controller and the at least one memory layers. Additionally, the memory-controller layer includes at least one external interface configured to transmit data to and from the memory module. Furthermore, the memory module can include an optical layer. The optical layer can be included in the stack and has a bus waveguide to transmit data to and from the at least one memory controller. The external interface can be an optical external interface which interfaces with the optical layer.

Abstract: Optically-coupled memory systems are disclosed. In one embodiment, a system memory includes a carrier substrate, and a controller attached to the carrier substrate and operable to transmit and receive optical signals, and first and second memory modules. The module substrate of the first memory module has an aperture formed therein, the aperture being operable to provide an optical path for optical signals between the controller and an optical transmitter/receiver unit of the second memory module. Thus, the system memory provides the advantages of “free space” optical connection in a compact arrangement of memory modules. In an alternate embodiment, the first memory module includes a beam splitter attached to the module substrate proximate the aperture. In another embodiment, the first and second memory modules are staged on the carrier substrate to provide an unobstructed path for optical signals.

Abstract: A memory test system is disclosed. The memory system includes a memory device, a tester generating a clock signal and a test signal for testing the memory device, and an optical splitting module. The optical splitting module comprises an electrical-optical signal converting unit which converts each of the clock signal and the test signal into an optical signal to output the clock signal and the test signal as an optical clock signal and an optical test signal. The optical splitting unit further comprises an optical signal splitting unit which splits each of the optical clock signal and the optical test signal into n signals (n being at least two), and an optical-electrical signal converting unit which receives the split optical clock signal and the split optical test signal to convert the split optical clock signal and the split optical test signal into electrical signals used in the memory device.

Abstract: The memory module includes a plurality of memory devices, a first connector and a second connector. The first connector is disposed at a first position on the memory module. The first connector is configured to carry low-speed signals for the memory devices. The second connector is disposed at a second position on the memory module, different from the first position. The second connector is configured to carry high-speed signals for at least one of the memory devices. The high-speed signals are a higher speed form of signaling than the low-speed signals. The memory system may include at least one slot electrically connected to a chip set and at least one memory module electrically connected to the slot via the first connector. A transmission line such as a fiber optic cable electrically connects the second connector and the chip set.

Abstract: A detector circuit for detecting an external manipulation of an electrical circuit. The detector circuit includes a digital circuit which is sensitive to at least one of the effects of ionizing radiation or fluctuations of a supply voltage, and the output state of the digital circuit is indicative of an attack.

Abstract: A memory module having a high data processing rate and high capacity is provided. The memory module may include a memory chip, a controller controlling an operation of the memory chip, an optical detector converting an external input signal into an internal input signal to transmit the converted signal to the controller, and an optical generator converting an internal output signal received from the controller into an external output signal. The optical detector converts an external input optical signal into an internal input signal to transmit the converted signal to the controller. The optical generator converts an internal output signal received from the controller into an external output optical signal.

Abstract: The invention provides a semiconductor device where data can be written after the production and forgery caused by rewriting of data can be prevented, and which can be manufactured at a low cost using a simple structure and an inexpensive material. Further, the invention provides a semiconductor device having the aforementioned functions, where wireless communication is not blocked by the internal structure. The semiconductor device of the invention has an organic memory provided with a memory cell array including a plurality of memory cells, a control circuit for controlling the organic memory, and a wire for connecting an antenna. Each of the plurality of memory cells has a transistor and a memory element. The memory element has a structure where an organic compound layer is provided between a first conductive layer and a second conductive layer. The second conductive layer is formed in a linear shape.

Abstract: A memory module may include at least one memory package including an optical signal input/output (I/O) unit and a first optical beam path and a printed circuit board (PCB) on which the memory package is mounted. The PCB may have a second optical beam path configured to transmit an optical signal to the optical signal I/O unit. The memory module may further include a connecting body configured to mount the memory package on the PCB and match a refractive index of the first optical beam path with a refractive index of the second optical beam path.

Abstract: A memory module having a high data processing rate and high capacity is provided. The memory module may include a memory chip, a controller controlling an operation of the memory chip, an optical detector converting an external input signal into an internal input signal to transmit the converted signal to the controller, and an optical generator converting an internal output signal received from the controller into an external output signal. The optical detector converts an external input optical signal into an internal input signal to transmit the converted signal to the controller. The optical generator converts an internal output signal received from the controller into an external output optical signal.

Abstract: Disclosed are embodiments of a multi-chip assembly including optically coupled die. The multi-chip assembly may include two opposing substrates, and a number of die are mounted on each of the substrates. At least one die on one of the substrates is in optical communication with at least one opposing die on the other substrate. Other embodiments are described and claimed.

Abstract: The invention encompasses beam expanders and methods of using such beam expanders. A beam expander according to the present invention may advantageously be used with an interferometer. Beam expanders according to the present disclosure contain at least an input and an output lens, with the output lens having a plano-convex arrangement such that the surface of the output lens is optically flat and can be used as the reference surface in a Fizeau interferometer. The beam expander may also encompass a housing, a partially reflective coating and an anti-reflective coating.

Abstract: In a method for manufacturing a flexible memory device and semiconductor device, a stack including an element layer and an insulating layer which seals the element layer is formed over a substrate having a separation layer, and the stack is separated from the separation layer. The element layer includes a memory element having a layer containing an organic compound between a pair of electrodes, a first electrode layer and a second electrode layer, and at least one of the pair of electrode layers is formed using an alloy layer containing tin. The flexible memory device and semiconductor device include a memory element having a layer containing an organic compound between a pair of electrodes, a first electrode layer and a second electrode layer, in which at least one of the pair of electrode layers is formed using an alloy layer containing tin.

Abstract: Optically-coupled memory systems are disclosed. In one embodiment, a system memory includes a carrier substrate, and a controller attached to the carrier substrate and operable to transmit and receive optical signals, and first and second memory modules. The module substrate of the first memory module has an aperture formed therein, the aperture being operable to provide an optical path for optical signals between the controller and an optical transmitter/receiver unit of the second memory module. Thus, the system memory provides the advantages of “free space” optical connection in a compact arrangement of memory modules. In an alternate embodiment, the first memory module includes a beam splitter attached to the module substrate proximate the aperture. In another embodiment, the first and second memory modules are staged on the carrier substrate to provide an unobstructed path for optical signals.

Abstract: A memory device includes a bit cell including an adjustable transmittance component having a first side and a second side. The adjustable transmittance component has an adjustable transmittance state representative of a bit value of the bit cell. The memory device further includes a photon detector optically coupled to a second side of the adjustable transmittance component. A technique related to the memory device includes determining a transmittance state of the adjustable transmittance component and providing a bit value for the bit cell based on the transmittance state. Another technique related to the memory device includes determining a bit value to be stored at the bit cell and configuring the adjustable transmittance component to have a transmittance state corresponding to the bit value.

Abstract: A memory module is formed of multiple memory chips and an optical interface chip fixed on a substrate. The chips are interconnected by proximity communication (PxC) in which each chip includes transmitting and receiving elements, such as electrical pads which form capacitively coupled links when the chips are placed together with their pads facing each other. The PxC links may be directly between the chips or through an intermediate passive bridge chip. The interface chip is coupled to an external optical channel and includes converters between optical and electrical signals, control circuitry, buffers, and PxC elements for communicating with the memory chips. The array of memories may be a linear or two-dimensional array around the interface chip forming a redundant PxC network, optionally with redundant PxC connections. Multiple rectangular memory chips may present their narrow sides to the interface chip to maximize bandwidth.

Abstract: Optically-coupled memory systems are disclosed. In one embodiment, a system memory includes a carrier substrate, and a controller attached to the carrier substrate and operable to transmit and receive optical signals, and first and second memory modules. The module substrate of the first memory module has an aperture formed therein, the aperture being operable to provide an optical path for optical signals between the controller and an optical transmitter/receiver unit of the second memory module. Thus, the system memory provides the advantages of “free space” optical connection in a compact arrangement of memory modules. In an alternate embodiment, the first memory module includes a beam splitter attached to the module substrate proximate the aperture. In another embodiment, the first and second memory modules are staged on the carrier substrate to provide an unobstructed path for optical signals.

Abstract: In some embodiments, a method, apparatus and system for n-dimensional sparse memory using serial optical memory are presented. In this regard, a memory device is introduced to circulate a signal among a plurality of optical emitters and receivers. Other embodiments are also disclosed and claimed.

Abstract: In some embodiments, a method, apparatus and system for global shared memory using serial optical memory are presented. In this regard, a memory device is introduced to circulate a signal among a plurality of optical emitters and receivers. Other embodiments are also disclosed and claimed.

Abstract: A controller converts a parallel command signal and address signal, or a parallel write data signal into a first serial signal, and outputs the converted signal as a first optical signal with a single wavelength to a memory device via an optical transmission line. The memory device converts the first optical signal into the original parallel command signal, address signal, and write data signal, and outputs the converted parallel signals to a memory unit. The memory device converts a parallel read data signal from the memory unit into a second serial signal, and outputs the converted signal to the controller via the optical transmission line as a second optical signal with a single wavelength. It is unnecessary to transmit the optical signal using an optical multiplexer, an optical demultiplexer, etc., thereby improving transmission rate of signals transmitted between the controller and the memory device at minimum cost.

Abstract: A semiconductor integrated circuit capable of protection from card hacking, by which erroneous actions are actively induced by irradiation with light and protected secret information is illegitimately acquired, is to be provided. Photodetectors, configured by a standard logic process, hardly distinguishable from other circuits and consumes very little standby power, are mounted on a semiconductor integrated circuit, such as an IC card microcomputer. Each of the photodetectors, for instance, has a configuration in which a first state is held in a static latch by its initializing action and reversal to a second state takes place when semiconductor elements in a state of non-conduction, constituting the static latch of the first state, is irradiated with light. A plurality of photodetectors are arranged in a memory cell array. By incorporating the static latch type photodetector into the memory array, they can be arranged inconspicuously.

Abstract: Various embodiments of the present invention are directed to stacked memory modules. In one embodiment of the present invention, a memory module comprises at least one memory-controller layer stacked with at least one memory layer. Fine pitched through vias (e.g., through silicon vias) extend approximately perpendicular to a surface of the at least one memory controller through the stack providing electronic communication between the at least one memory controller and the at least one memory layers. Additionally, the memory-controller layer includes at least one external interface configured to transmit data to and from the memory module. Furthermore, the memory module can include an optical layer. The optical layer can be included in the stack and has a bus waveguide to transmit data to and from the at least one memory controller. The external interface can be an optical external interface which interfaces with the optical layer.

Abstract: A microcomputer includes a circuit block; a nonvolatile memory configured to store optimization data for optimization of an operation of the microcomputer; and an optimization circuit configured to read out memory optimization data as a part of the optimization data from the nonvolatile memory in synchronization with a first frequency clock signal as an first clock signal to optimize an operation of the nonvolatile memory, and then to read out circuit block optimization data as another part of the optimization data from the nonvolatile memory in synchronization with a second frequency clock signal as the first clock signal to optimize an operation of the circuit block. The frequency of the first frequency clock signal is lower than that of the second frequency clock signal.

Abstract: The invention relates to an information carrier (101) intended to be read and/or written by a periodic array of light spots, said information carrier (101) comprising a data area (105) defined by a set of elementary data areas, a first periodic structure (108) intended to interfere with said periodic array of light spots for generating a first moiré pattern, a second periodic structure (109) intended to interfere with said periodic array of light spots for generating a second moiré pattern, said second periodic structure (109) being arranged perpendicularly to said first periodic structure (108). The invention also relates to an apparatus for reading and/or writing said information carrier (101).

Abstract: The invention relates to an information carrier, and a system for positioning such an information carrier in an apparatus. This system comprises an optical element (102) for generating a periodic array of light spots (103) intended to be applied to an information carrier (101), said information carrier (101) comprising a first periodic structure (108) intended to interfere with said periodic array of light spots (103) for generating a first Moiré pattern, and a second periodic structure (109) intended to interfere with said periodic array of light spots (103) for generating a second Moiré pattern, analysis means for deriving from said first and second Moiré patterns, the angle value (S) between said periodic array of light spots (103) and said information carrier (101), and actuation means (AC1-AC2-AC3) for adjusting the angular position of said information carrier (101) with respect to said array of light spots (103), from control signals (114) derived based on said angle value (S).

Abstract: A memory controller multiplexes access signals each consisting of a plurality of bits as optical signals and outputs the multiplexed optical signals. At this time, the optical signals whose wavelengths differ depending on memory devices are generated. A memory interface unit demultiplexes the multiplexed optical signals into the original optical signals and converts the demultiplexed optical signals into electrical signals. The memory interface unit determines to which of the memory devices the electrical signals resulting from the conversion should be outputted, according to the wavelengths of the demultiplexed optical signals. This frees the memory controller from a need for transmitting to the memory interface unit a signal for identifying the memory device. The memory interface unit need not include a decoding circuit for identifying the memory device.

Abstract: A memory device includes a semiconductor substrate in which memory circuitry has been fabricated. An address converter and a control signal converter are coupled to an address decoder and control logic, respectively. The address and control converters are operable to receive and convert optical address and control signals, respectively, into corresponding electrical address signals applied to the address decoder and control signals applied to the control logic. A read/write circuit on the substrate is coupled to a data converter formed in the substrate. The data converter is operable to receive and convert optical write data signals into corresponding electrical data signals to be applied to the read/write circuit and to receive and convert electrical read data signals into corresponding optical read data signals.

Abstract: Optically-coupled memory systems are disclosed. In one embodiment, a system memory includes a carrier substrate, and a controller attached to the carrier substrate and operable to transmit and receive optical signals, and first and second memory modules. The module substrate of the first memory module has an aperture formed therein, the aperture being operable to provide an optical path for optical signals between the controller and an optical transmitter/receiver unit of the second memory module. Thus, the system memory provides the advantages of “free space” optical connection in a compact arrangement of memory modules. In an alternate embodiment, the first memory module includes a beam splitter attached to the module substrate proximate the aperture. In another embodiment, the first and second memory modules are staged on the carrier substrate to provide an unobstructed path for optical signals.

Abstract: A memory device includes a semiconductor substrate in which memory circuitry has been fabricated. An address converter and a control signal converter are coupled to an address decoder and control logic, respectively. The address and control converters are operable to receive and convert optical address and control signals, respectively, into corresponding electrical address signals applied to the address decoder and control signals applied to the control logic. A read/write circuit on the substrate is coupled to a data converter formed in the substrate. The data converter is operable to receive and convert optical write data signals into corresponding electrical data signals to be applied to the read/write circuit and to receive and convert electrical read data signals into corresponding optical read data signals.

Abstract: Optically-coupled memory systems are disclosed. In one embodiment, a system memory includes a carrier substrate, and a controller attached to the carrier substrate and operable to transmit and receive optical signals, and first and second memory modules. The module substrate of the first memory module has an aperture formed therein, the aperture being operable to provide an optical path for optical signals between the controller and an optical transmitter/receiver unit of the second memory module. Thus, the system memory provides the advantages of “free space” optical connection in a compact arrangement of memory modules. In an alternate embodiment, the first memory module includes a beam splitter attached to the module substrate proximate the aperture. In another embodiment, the first and second memory modules are staged on the carrier substrate to provide an unobstructed path for optical signals.