Patent Description:
Optical cables have the advantage over conventional copper cables that a higher signal and/or data transmission rate can be achieved. Hence, in particular with the emergence of ultra high definition visual systems, optical cables are heavily relied upon. For transmitting different data, for example input and output data of an interactive display, a cable may be provided with more optical fibers arranged parallel to one another in the core section. Thus, a connection port for each optical fiber needs to be provided, increasing the space requirements of the cable system.

In <CIT> optical die structures and associated package substrates are generally described. In one example, an electronic device includes a package substrate having a package substrate core, a dielectric layer coupled with the package substrate core, and one or more input/output (I/O) optical fibers coupled with the package substrate core or coupled with the build-up dielectric layer.

In <CIT> the wide bandwidth channel to a subscriber of an optical fiber cable TV system, and the narrow bandwidth return channel from the subscriber are wavelength division multiplexed over a single fiber.

<CIT> deals with a concentric core optical fiber that provides for the simultaneous but independent transmission of signals over a single optical fiber. The concentric optical fiber is constructed of a single mode or multimode inner optical fiber defined by a core and an outer optical fiber defined by an additional cladding.

A further concentric optical cable and connector capable of full duplex transmission of optically encoded information is disclosed in <CIT>.

<CIT> discloses a low-speed and high-speed interchangeable optical fiber which allows the transmission of both a low-speed signal and a high-speed signal by using the same optical transmitter. The optical fiber includes a first core, first clad, third clad, second core and second clad successively from the central part toward the outer peripheral part.

Therefore, it is the object of the invention to provide an easier to maintain optical cable with low space requirements.

By the inventive solution an optical cable is provided that comprises two channels, wherein the second channel surrounds the first channel. Therefore, reducing the space requirements of the optical cable and consequently the cable system. A single connection port may be provided for the connection of the inventive optical cable instead of having a separate connection port for each channel. Furthermore, each channel can be optimized for their respective tasks and thus over-engineering of the optical cable can be prevented. Hence, the inventive optical cable provides a compact and cost efficient design.

The invention can be improved further by the following features, which are independent from one another, with respect to their respective technical effects and which can be combined arbitrarily.

For example according to a first advantageous embodiment, the first channel may form a forward channel having a first forward signal and/or data bandwidth moving in the cable direction. The second channel may form a backward channel, having a second backward signal and/or data bandwidth moving opposite to the forward channel. Hence, a bidirectional optical cable is provided for transmitting signal and/or data input and output between two units, such as a processing unit and an output unit.

The core section is radially surrounded by the at least one optical fiber layer, so that a symmetrical coaxially arranged optical cable can be provided, facilitating the connection to complementary connection parts of the units.

The core section comprises at least one glass optical fiber. With a glass optical fiber a high-speed signal and/or data transmission can be achieved. The core section may preferably comprise a bundle of glass optical fibers.

A cladding is arranged between a fiber core of the at least one optical fiber in the core section and the at least one optical fiber layer. The cladding may comprise at least one layer of a lower refractive index in comparison to the fiber core material in the core section and/or the optical fiber layer. The cladding may improve transmission of the fiber and prevent any interference between the core section and the optical fiber layer.

The optical fiber layer comprises a polymer optical fiber material, such as acrylic glass and/or Polystyrene. The polymer optical fiber is characterized by its low price and high robustness under bending and stretching.

The diameter of the optical fiber layer, particularly the outer diameter, may be about <NUM>. Thus, the outer diameter is not too large, so that the damage of the optical fiber layer due to bending and/or stretching of the cable may be reduced.

The optical fiber layer may preferably be surrounded by an outer cladding for further improving the signal and/or data transmission of the optical fiber layer. Preferably, the optical fiber layer is sandwiched between the cladding and the outer cladding. The optical fiber layer, cladding and outer cladding can then form an optical waveguide with a pipe cross section.

Advantageously, the signal and/or data bandwidth of the first channel may be different to the signal and/or data bandwidth of the second channel. Hence, an optical cable with an asymmetric signal and/or data bandwidth can be provided. Preferably, the signal and/or data bandwidth of the second channel may be smaller than the bandwidth of the first channel. Hence, the first channel may be capable of transmitting high-speed data and/or signals, such as image output data of an ultra high definition imaging system and the second channel may be adapted to transmit low speed data and/or signals. Therefore, the channels may be optimized for their respective tasks and over-engineering may be further prevented.

The at least one optical fiber may be a single-mode optical fiber, wherein the fiber core diameter is much smaller than the thickness of the cladding. The fiber core diameter may be about <NUM> and the outer diameter of the cladding may be about <NUM>. Single-mode optical fibers have the advantage that even at long distances, i.e. longer than about <NUM>, a low signal and/or data loss can be achieved. Furthermore, a high bandwidth can be achieved even at a longer distance.

Alternatively, the at least one optical fiber may be a multi-mode optical fiber, wherein the fiber core diameter is larger than the fiber core diameter of a single-mode optical fiber. The fiber core diameter of the multi-mode optical fiber can be around <NUM> and the outer diameter of the cladding may be about <NUM>. Compared to single-mode optical fibers a lower maximal bandwidth is possible with multi-mode optical fibers. However, multi-mode optical fibers may have its advantages in a simpler and low cost production. Furthermore, the termination of the optical fiber may be easier since the fiber core diameter is larger. In particular, at short distances multi-mode optical fibers can achieve a high bandwidth.

The at least one multi-mode optical fiber can be in a step index configuration. The step index optical fiber may have a refractive index profile characterized by a uniform refractive index within the fiber core and a sharp decrease in refractive index at the fiber core-cladding interface and can be for example made by doping high-purity fused silica glass with different concentrations of materials like titanium, germanium or boron. The manufacturing of a step index multi-mode optical fiber may be easier and may involve fewer costs than a graded index multi-mode optical fiber.

Alternatively, the at least one multi-mode optical fiber can be in a graded index configuration, such as an "OM5" optical fiber. The graded index optical fiber may have a fiber core with a refractive index that decreases with increasing radial distance from the optical axis of the fiber. Hence, the light rays follow a sinusoidal, particularly a parabolic profile. This profile results in continual refocusing of the rays in the fiber core and consequently minimizing modal dispersion. Furthermore, the information carrying capacity may be increased, compared to the step index multi-mode optical fiber.

According to a further aspect not forming a part of the invention, the optical fiber layer and the at least one optical fiber may be rigidly attached to one another, for example the core section may be coated by the optical fiber layer. With the rigid attachment, loose parts may be prevented and the optical fiber layer may serve as a robust shell for the core section.

According to a further aspect of the invention, the optical fiber layer is removably attached to the core section. The optical fiber layer may be formed as a pipe capable of receiving the core section. The core section may be movable essentially parallel to the cable direction relative to the optical fiber layer. In this embodiment, the core section and/or the optical fiber layer may be removed and replaced independently from the other. Thus, if a part gets damaged, the damaged part can be replaced while the other parts may still be intact.

The optical fiber layer may preferably be formed by extrusion.

According to a further aspect of the invention, the inventive optical cable can be used to transmit at least one of a video, image and audio data and/or signal through the first channel. The first channel may preferably have a high-speed signal and/or data transmission, so that in particular an ultra high definition image or video can easily be displayed.

According to another aspect of the invention, the inventive optical cable can be used to transmit a user input signal and/or data through the second channel. The user input may be at least one of an audio, video and touch event. For example, an interface may be controlled by voice, gestures and/or touch, wherein this information is sent through the second channel. The second channel may preferably have a lower speed signal and/or data transmission than the first channel since the user input signals and/or data do not require such a high bandwidth, further reducing the costs of the optical cable, by preventing over-engineering.

In the following, the optical cable according to the invention is explained in greater detail with reference to the accompanying drawings, in which exemplary embodiments are shown.

In the figures, the same reference numerals are used for elements which correspond to one another in terms of their function and/or structure.

According to the description of the various aspects and embodiments, elements shown in the drawings can be omitted if the technical effects of these elements are not needed for a particular application, and vice versa, i.e. elements that are not shown or described with reference to the figures but are described above can be added if the technical effect of those particular elements is advantageous in a specific application.

An optical cable <NUM> according to the invention is shown in <FIG>, wherein the optical cable <NUM> connects two units <NUM>, <NUM>. The units <NUM>, <NUM> and the optical cable <NUM> form a cable system <NUM>. The unit <NUM> may be a processing unit <NUM> for generating data and the unit <NUM> may be an output unit <NUM>, such as a display and/or speaker system for outputting the data generated by the processing unit <NUM>. Therefore, the optical cable <NUM> transmits data in a cable direction <NUM> from the processing unit to the output unit <NUM> through a first channel <NUM>.

The first channel <NUM> is formed by at least one optical fiber <NUM> at a core section <NUM> of the optical cable <NUM>. In this exemplary embodiment, the core section <NUM> is formed by a single optical fiber <NUM>. However, in an alternative not shown embodiment, the core section <NUM> may be formed by a bundle of optical fibers <NUM>. Preferably, the optical fiber <NUM> is a glass optical fiber <NUM>, which is capable of a high-speed transmission of signals and/or data. Thus, the information can be transmitted from the processing unit <NUM> to the output unit <NUM> at a high speed of up to about <NUM> Gbps.

The output unit <NUM> may be an interactive unit working as an interface <NUM>, for a user <NUM> to send commands to the processing unit <NUM>. The interface <NUM> may be controlled by at least one of a video, audio and touch event. For example, the interface <NUM> may be a touch sensitive display transmitting information of at least one of position, pressure and motion to the processing unit <NUM>. Additionally or alternatively, the interface <NUM> may be voice controlled, wherein the user's audio commands are transmitted to the processing unit <NUM>. The bandwidth required to transmit said information to the processing unit <NUM> is lower than the requirements for transmitting the signals and/or data from the processing unit <NUM> to the output unit <NUM>.

For transmitting user input <NUM> to the processing unit <NUM>, a second channel needs to be provided. In known cable systems <NUM>, a separate optical cable <NUM> may be provided, each forming a single channel. However, this requires a lot of space since a separate connection port has to be provided at the units <NUM>, <NUM> for each channel, further increasing the size and costs of the cable system <NUM>.

The function and structure of the inventive optical cable <NUM> is now explained in greater detail with reference to <FIG> showing a cross section <NUM> perpendicular to the cable direction <NUM> of the inventive optical cable <NUM>.

In order to have an optical cable <NUM> with a compact and cost efficient design, a second channel <NUM> is formed by at least one optical fiber layer <NUM>, surrounding the core section <NUM>. Thus, an optical cable <NUM> with coaxially arranged channels is provided. The connection ports for each channel may also be consequently coaxially arranged, taking up less space than having two separate connection ports.

In this exemplary embodiment, the first channel <NUM> forms a forward channel <NUM> and the second channel <NUM> forms a backward channel <NUM> transmitting signals and/or data in opposite directions. Therefore, a bidirectional optical cable <NUM> is produced. The second channel <NUM> can be designed according to its requirements, independently from the first channel <NUM>, preventing over-engineering of the optical cable <NUM> and further decreasing the costs of the optical cable <NUM>.

The core section <NUM> preferably comprises a glass optical fiber <NUM> with a fiber core <NUM> and a cladding <NUM> radially surrounding the fiber core <NUM>. The cladding <NUM> can further improve the transmission through the fiber core <NUM>. The cladding <NUM> may comprise multiple layers of different cladding materials and have a lower refractive index as the fiber core <NUM>. The cladding <NUM> causes light to be confined to the fiber core <NUM> by total internal reflection at the boundary between the cladding <NUM> and the fiber core <NUM>. Hence, the light in the first channel <NUM> is prevented to pass through the cladding <NUM> and possibly cause an interference in the second channel.

Depending on the application requirements, the optical fiber <NUM> may be a single mode or multi-mode optical fiber. Single-mode optical fibers have the advantage that even at long distances, i.e. longer than about <NUM>, a low signal and/or data loss can be achieved. Furthermore, a high bandwidth can be achieved even at a longer distance. Compared to single-mode optical fibers, a lower maximal bandwidth is possible with multi-mode optical fibers. However, multi-mode optical fibers may have its advantages in a simpler and low cost production.

Furthermore, the termination of the optical fiber may be easier, since the fiber core diameter is larger. In particular, at short distances, multi-mode optical fibers can achieve a high bandwidth.

The second channel <NUM> is formed by the at least one optical fiber layer <NUM> that surrounds the core section <NUM>. In this exemplary embodiment, the optical fiber layer <NUM> is in intimate contact with the cladding <NUM>. Therefore, the cladding <NUM> also serves as an inner cladding <NUM> for the second channel <NUM>. The optical fiber layer <NUM> and the optical fiber <NUM> may be attached rigidly to one another, preventing any relative movement between these two components. The optical fiber layer <NUM> and the optical fiber <NUM> may be bonded adhesively to one another. Alternatively, the optical fiber layer <NUM> may be a separate part with a pipe shaped cross section, adapted to receive the optical fiber <NUM>. The optical fiber <NUM> may be movable relatively to the pipe shaped optical fiber layer <NUM>, so that a damaged part can be removed and replaced, without affecting the other part.

The optical fiber layer <NUM> may preferably comprise a polymer optical fiber <NUM> such as PMMA. This may be of particular advantage since polymer optical fibers <NUM> have proven to have a higher straining and bending tolerance than glass optical fibers and are cheaper. Since the transmission speed requirements of the second channel <NUM> are relatively low compared to the first channel <NUM> in this exemplary embodiment, the requirements can be satisfied by the polymer optical fiber <NUM>.

An outer cladding <NUM> may be provided surrounding the optical fiber layer <NUM>, working as an outer boundary for containing the light waves and causing refraction. This further improves the transmission through the optical fiber layer <NUM>. Further components can be provided which are not shown in the figures. For example, a coating may be provided that surrounds the outer cladding, in order to reinforce the optical fiber layer <NUM> and the fiber core <NUM>. The coating may be a layer of plastic and may adsorb shocks as well as provide extra protection against excessive cable bends. Furthermore, a bundle of strengthening fibers may be provided, helping to protect the optical fiber layer <NUM> and/or the fiber core <NUM> against crushing forces and excessive tension during installation. In addition, a cable jacket may be provided, sheathing the other components of the optical cable <NUM>.

Claim 1:
Optical cable (<NUM>) comprising a core section (<NUM>) with at least one optical fiber (<NUM>) extending in a cable direction (<NUM>) forming a first channel (<NUM>) for transmitting signal and/or data, wherein the core section (<NUM>) is surrounded by at least one optical fiber layer (<NUM>) forming a second channel (<NUM>) for transmitting signal and/or data, the core section (<NUM>) and the at least one optical fiber layer being arranged coaxially with one another, characterized in that the at least one optical fiber (<NUM>) and the at least one optical fiber layer (<NUM>) are attached removably to one another.