Patent Description:
The VFL illuminates the core of the fiber optical cable with laser light in the visual spectrum. Typically, red laser light is used. When the light is incident on a break in the core of the fiber optical cable, the light will "leak" from the break and, depending on the jacket arrangement, will be visible at the break in the core through the cladding and jacket of the fiber optical cable. During illumination, a person may visually inspect the cable for breaks by looking for leaking light. This technique is most applicable for testing fiber optical cables with relatively short lengths, such as lengths of <NUM> meters or less.

Currently available VFLs are hand-held tools that include all functional components of the VFL in a housing, such as electronics, a power source (e.g., batteries), and the emitting laser. The port for the connector of the fiber optic cable is mounted to the housing. A button board that retains user control buttons is also mounted to the housing. Some VFLs may be operated to continuously emit laser light and/or to pulse the laser light. Most VFLs may be used to test multimode fibers and single mode fibers. VFL functionality also may be found in more advanced test equipment, such as an optical power meter or an optical time-domain reflectometer (OTDR). <CIT> concerns a portable optical measuring instrument. <CIT> concerns an optical network communication system with embedded optical time domain reflectometer and method of operation thereof. <CIT> concerns an optical fiber test apparatus with combined light measurement and fault detection. <CIT> concerns a VCSEL fault location apparatus and method. <CIT> concerns a high density optical transceiver.

The conventional VFL form-factor is portable, but is often inconvenient to use to test cables that have been connected to rack-mounted optical network devices (e.g. network data switches). An exemplary commercially available VFL while in use in a data center is shown in <FIG>. As can be seen, one problem with conventional VFLs is that the VFL must be physically supported in a tight space and the operator may need to hold the connector into the port of the VFL. This can be a difficult task if the operator is not assisted by another person and needs to leave the location of the VFL to inspect the cable being tested or engage in other activities involving the user's hands.

Disclosed is a VFL in a small form factor, such as a form factor compatible with IEEE's Multi-Source Agreement (MSA) receptacle for Small Form Factor (SFF) electronics, according to claim <NUM>. This is the form factor according to which many hot-pluggable datacomm-style transceivers are made. The disclosed VFL fits in and receives operating power from an industry standard port (e.g., an SFF port) that is normally used for optical communication devices. Optionally, the VFL receives communication information from the port in addition to operating power.

The invention defines a visual fault locator including a housing; a receptacle retained by the housing and configured to receive a connector of a fiber optic cable under test; a light source retained by the housing and positioned relative to the receptacle to emit light into a core of the fiber optic cable under test. The emitted light is configured to detect a break in the core of the fiber optic cable under test by being visually detectable through a jacket of the fiber optic cable under test at a point of a break in the core and the housing is physically configured so as to be removably installed in a port of a host device. An interface in the form of an electrical connector is retained by the housing. The interface mates with a corresponding connector of the host device, the visual fault locator is not including a power source and receives operational power for the light source from the host device via the interface, wherein the visual fault locator comprises a control circuit that controls operation of the light source, the control circuit is powered by the operational power from the host device via the interface, the visual fault locator further comprises a physical user input retained by the housing and operable by a user to control the control circuit to change operating states of the light source, and the visual fault locator is not capable of transmitting communications data in an optical signal.

Embodiments will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout.

Referring to <FIG>, illustrated is a schematic block diagram of a visual fault locator (VFL) <NUM> according to aspects of the disclosure. The VFL <NUM> includes a receptacle <NUM> to which a connector (also referred to as a terminus) of a fiber optic cable may be installed and retained without further mechanical support. In one embodiment, the receptacle <NUM> latches the connector therein to reduce the possibility that the connector unintentionally separates from the receptacle <NUM>. A fiber optic cable that is connected to the VFL <NUM> for testing will be referred to as a cable under test. The receptacle <NUM> may be an industry standard receptacle for fiber optic cable connectors such as, but not limited to, an LC receptacle, an ST receptacle, or an FC receptacle.

The VFL <NUM> further includes a light source <NUM>. The light source <NUM> may include one or more light emitters, preferably one or more solid state light emitters. The light source <NUM> and the receptacle <NUM> are arranged so that, when a cable under test is connected to the receptacle <NUM>, light from the light source <NUM> is introduced into the terminal end of a core (including the filament) of the cable under test. The light will propagate along the cable under test and, if there is a break in the core, the light will escape from the core. This allows for visual inspection of the cable under test. The light source <NUM> may be any suitable device. The light source <NUM> may be, for example, a one or more laser diodes or one or more a vertical-cavity surface-emitting lasers (VCSELs). The VFL <NUM> need not have an optical receiver for detecting or demodulating data in an optical signal, but it is possible to include an optical receiver to provide for more advanced test capabilities. Also, the VFL <NUM> may not be capable of transmitting communications data in an optical signal, but it is possible to include an optical transmitter to provide for more advanced test capabilities.

The light source <NUM> may emit light in the visible spectrum such as, but not limited to, red light, green light, blue light or light of another color. In one embodiment, the VFL <NUM> may have multiple light emitters that are selectively turned on and off to change the wavelength of the emitted light (e.g., switch between red light and green light) or a light emitter that is capable of changing its emitted wavelength. The light source <NUM> alternatively may emit light outside the visible spectrum, in which case the operator may use an appropriate detector or wavelength changing glasses to inspect for a break in the cable under test.

Operations of the VFL <NUM> are controlled by electronics in the form of a control circuit <NUM>. The control circuit <NUM> may include a driver for driving the light source <NUM>. The control circuit <NUM> may receive control input signals from a user input <NUM>. The user input <NUM> may be one or more buttons, rotary dial switch, and/or switches, and may be used to control one or more operational states of the light source <NUM>. For example, the user input <NUM> may be used to control an on/off state of the light source <NUM>. In one embodiment, the light source <NUM> may be controlled to be either on or off. When on, the light source <NUM> steadily emits light and, when off, does not emit light. In another embodiment, the light source <NUM> may have one or more pulse modes in which the light source <NUM> emits light in pulses with a predetermined duty cycle. In one embodiment, the light source <NUM> may have a pulsed mode and/or a modulated mode in addition to on and off modes. In one embodiment, the output intensity of the light intensity of the light source <NUM> is fixed and cannot be varied by the user. In other embodiments, an output intensity of the light source <NUM> may be variable and controllable by the user through use of the user input <NUM>. In embodiments where the wavelength of the emitted light may be changed, the emitted wavelength may be controlled with the user input <NUM>. Also, the VFL <NUM> may be controlled or preconfigured programmed to emit light for a specified duration.

As indicated, the optical power of the light emitted by the light source <NUM> may be altered. In one embodiment, the emitter or emitters of the light source <NUM> may be driven to emit more or less light. In another embodiment, the light source <NUM> has two or more light emitters that are selectively operated (e.g., individually turned on or off and/or individually driven to emit more or less light) to vary the collective optical power of the light emitted by the light source <NUM>. For instance, the light source <NUM> may include an array or matrix or VCSELs or other light emitters. Each VCSEL may be individually controlled to emit light or not emit light, emit light that is pulsed or modulated, and/or emit light of varying intensity so as to collectively emit light with desired optical characteristics, such as optical power, intensity and/or wavelength. In one embodiment, the light source <NUM> may have an array or matrix of four VCSELs. It is contemplated that operating a single VCSEL in this arrangement may result in emitting light of a class <NUM> laser, which may be used to inspect for breaks in a fiber optic cable of about <NUM> meters in length. Similarly, operating two VCSELs in this arrangement may result in emitting light of a class <NUM> laser, which may be used to inspect for breaks in a fiber optic cable of about <NUM> kilometer in length. Operating four VCSELs in this arrangement may result in emitting light of a class <NUM> laser, which may be used to inspect for breaks in a fiber optic cable of about <NUM> kilometers in length. To maintain eye safety, the VFL <NUM> may include a light meter (e.g., a monitor diode) that monitors the optical power of the light emitted by the light source <NUM>. An output of the light meter may be input to the control circuit <NUM>, which uses the output value to regulate the light output by the light source <NUM> and/or limit the light output by the light source <NUM> to a predetermined threshold. In one embodiment, the operator may use eye safety equipment (e.g., light attenuating glasses) and control the VFL <NUM> to emit light above the predetermined threshold.

As mentioned, the VFL <NUM> is used to inspect for breaks in a cable under test. As used herein, the term break include full cracks in the core or filament of the cable under test, a partial crack in the core or filament of the cable under test, a hairline fracture in the core or filament of the cable under test, and a mircobend or other imperfection caused by manufacturing defect or otherwise in the core or filament of the cable under test. As will be understood, some breaks may not be visibly detectable if the output power of the light source <NUM> is relatively low. Therefore, depending on the length of the cable under test, there are times when it may be advantageous to increase the optical power of the light emitted by the light source <NUM> as described above.

As indicated, visually detecting light output from the cable under test at a break includes detection by the eyes of a human operator with or without an assistance device (e.g., wavelength changing glasses). As used herein, the terms visually detecting light and light that is visually detectable include detection by the aided or unaided eyes of a human operator or by a machine. Exemplary machines that may detect light output at a break in a cable under test may include a machine vision apparatus, a spectrum analyzer, or other system.

The VFL <NUM> does not have its own power source (e.g., one or more batteries) to operate the control circuit <NUM>, the user input <NUM> and the light source <NUM>. The VFL <NUM> relies on power from a host device, such as a data center switch. For this purpose, the VFL <NUM> has an interface <NUM> to the host. The interface <NUM> may be an electrical connector that mates with a corresponding connector of the host. In one embodiment, only power is received by the VFL <NUM> from the host and no communications are made between the VFL <NUM> and the host. In other embodiments, communications between the VFL <NUM> and the host may be made. For instance, some hosts may require devices that are installed in a port of the host to be an authorized device. In this case, the VFL <NUM> and the host may engage in a handshake routine to confirm that the VFL <NUM> is authorized. In other cases, a user may enable the port through a software interface with the host. In still other embodiments, control over the operation of the VFL <NUM> may be made using the software interface that communicates with the VFL <NUM> by way of the interface instead of or in addition to controlling the VFL <NUM> by way of the user input <NUM>. Following installation, the VFL <NUM> may receive power from the host. A ground connection between the VFL <NUM> and the host also may be made via the interface <NUM>. In one embodiment, and as explained in greater detail below, the interface <NUM> may be a small form factor (SFF) interface pursuant to the IEEE-defined Multi-Source Agreement (MSA) for SFF electronics. Other possible interfaces <NUM> include proprietary connectors, universal serial bus (USB) connectors, etc..

The VFL <NUM> may be self-contained. In this configuration, the VFL <NUM> has a housing that retains the receptacle <NUM>, the light source <NUM>, the control circuit <NUM>, the user input <NUM> and the interface <NUM>. The physical configuration also may conform to the SFF industry standard.

With additional reference to <FIG>, a representative embodiment of a self-contained VFL <NUM> is illustrated. <FIG> and <FIG> show the VFL <NUM> in isolation. <FIG> shows the VFL <NUM> with a cable under test <NUM> connected to the receptacle <NUM> of the VFL <NUM>. <FIG> show the VFL <NUM> retained by a host <NUM>.

In the illustrated embodiment, the VFL <NUM> physically and/or electrically conforms to the MSA for SFF electronics. The VFL <NUM> may further have a small form factor pluggable (SFP) configuration (e.g., so as to be hot-pluggable). Other MSA or non-MSA form factors are possible such as, but not limited to, an XFP form factor, an SFP form factor, a CFP, CFP2 or CFP4 form factor, a CXP form factor, a dual pluggable SFP form factor, etc. In accordance with the desired form factor, the VFL <NUM> has a housing <NUM> that is compatibly pluggable (including removable) into a coordinating port <NUM> (<FIG>) of the host <NUM>. The housing <NUM> of the illustrated embodiment includes a cast metal base <NUM> and a sheet metal top <NUM>. In the typical embodiment, the port <NUM> of the host <NUM> is arranged to mechanically receive and electrically interface with a data communications device to operatively establish optical data communications with a remote end over a fiber optical cable connected to the data communications device.

The VFL <NUM> may include a bail latch <NUM>. The bail latch <NUM> is shown in the latched position. When inserting or removing the VFL <NUM> from the port <NUM> of the host <NUM>, the bail latch <NUM> may be pivoted downward to disengage and/or allow release of a latching feature <NUM> (<FIG>) of the VFL <NUM> from a corresponding feature of the host <NUM>. In the illustrated position, the bail latch <NUM> may latch the latching feature <NUM> of the VFL <NUM> with the host <NUM>. In one embodiment, the bail latch <NUM> alternatively and/or additionally serves as a user input <NUM>. For this purpose, the position of the bail latch <NUM> is detectable by a sensor or switch of the VFL <NUM> and the sensed position serves as an input to the control circuit <NUM>.

The receptacle <NUM> of the VFL <NUM> of the illustrated embodiment is an LC receptacle. Accordingly, a connector <NUM> (<FIG>) of the cable under test <NUM> in the illustrated embodiment is an LC connector. Other receptacle and connector types may be used.

The user input <NUM> of the VFL <NUM> of the illustrated embodiment is a push button switch. Other types of user inputs <NUM> are possible, such as a capacitive membrane switch, a toggle switch, a rotary dial switch, etc. The user input <NUM> may be used to control the VFL <NUM> in the manners described above. Other ways to control the VFL <NUM> are discussed below. The user input <NUM> may be located adjacent the receptacle <NUM> so as to be accessible when the VFL <NUM> is installed in the port <NUM> of the host <NUM>. According to the illustrated embodiment, the VFL <NUM> includes two industry standard receptacles for fiber optic connectors. In this case, a first of the standard receptacles is associated with the light source <NUM> and forms the receptacle <NUM>, and a second of the standard receptacle retains the user input <NUM>. For this purpose, the user input <NUM> is configured to fit and latch into the physical configuration of the second standard receptacle. In one embodiment, the user input <NUM> may have a locking feature to prevent inadvertent removal of the user input <NUM>.

Different interactions with the user input <NUM> may be associated with different control functions. For example, in the embodiment where the user input <NUM> is a push button switch, such as found in the illustrated embodiment, different interactions with the push button may be associated with different control functions. For example, if the VFL <NUM> has on and off modes, short depressions of the push button may alternate between turning the light source <NUM> on and off. If the VFL <NUM> has an on mode, an off mode and a pulsed or modulated mode, short depressions of the push button may cycle through these modes. Long depressions of the push button or a predetermined sequence of depressions may control the output intensity of the light source <NUM> (e.g., to increase or decrease the optical power of the light source <NUM>), control the wavelength of the emitted light, etc..

The interface <NUM> to the host may be an industry standard electrical connector. As indicated, the VFL <NUM> need not engage in communications with the host <NUM>, but may receive operating power via the interface <NUM>. A ground connection also may be made via the interface <NUM>. In the embodiment where the VFL <NUM> is configured according to MSA SFF specification, the interface <NUM> of the VFL <NUM> may connect to power and ground connectors of a coordinating connector in the host. Additional contact may be present to exchange digital diagnostic data messages with the host, through which control of the VFL <NUM> may be made. The connection of the interface <NUM> with the host <NUM> is not used, however, for the exchange of communications data as would be found with a data communications device configured in accordance with MSA SFF specifications.

The VFL <NUM> may further include a sensor <NUM> (<FIG>) to detect presence or absence of the connector <NUM> in the receptacle <NUM>. If the connector <NUM> is present, then the light source <NUM> may be enabled so as to emit light. If the connector <NUM> is not present, then the light source <NUM> may be disabled and prevented from emitting light. This may assist in preventing unintended exposure of laser light to a user. The sensor <NUM> may be a switch or an optical sensor. In another embodiment, the sensor <NUM> may be a continuity sensor that electrically detects presence of a conductive part of the connector <NUM>.

The host <NUM> includes one or more ports <NUM> that are compatible with the form factor of the VFL <NUM>. In the illustrated embodiment, the ports <NUM> are SFP ports <NUM> that may physically receive and power the VFL <NUM>. Therefore, during operation of the VFL <NUM> to test the cable under test <NUM>, the host <NUM> physically supports the VFL <NUM> and the VFL <NUM>, in turn, physically retains and supports the cable under test <NUM>. This frees the hands of the user to complete other tasks. Additionally, the user may move away from the terminal end of the cable under test <NUM> to visually inspect portions of the cable under test <NUM> that are not visible from the location of the terminal end. In one embodiment, the host <NUM> is a rack mounted data center switch (e.g., as illustrated) or other type of network equipment.

An exemplary method of using the VFL <NUM> will be described. It will be understood that other ways of using the VFL <NUM> are possible, including an embodiment where the VFL <NUM> remains connected to the port <NUM>. In the exemplary method, the user disconnects a fiber optic cable that is suspected of having a break from a datacomm SFP that is in a network switch port <NUM>. The user then removes the datacomm SFP from the network switch port <NUM>. The VFL <NUM> is then installed in the network switch port <NUM> from which the datacomm SFP was removed. Alternatively, if the network switch has a free port, it is possible that the datacomm SFP may remain in place and the VFL <NUM> is installed in the free port.

Following installation of the VFL <NUM>, the fiber optic cable that was disconnected (i.e., the cable under test <NUM>) may be connected to the receptacle <NUM> of the VFL <NUM>. The user then activates the light source <NUM> by interaction with the user input <NUM> and, if appropriate, adjusts the light source <NUM> in terms of intensity, color and/or other operational mode (e.g., an on mode versus a pulse mode). The user may then visually inspect the cable under test <NUM> for breaks. If a break is found, then the cable may be replaced or repaired, and the new or repaired cable may be tested for faults. Thereafter, the VFL <NUM> may be removed and the datacomm SFP may be returned to the network switch port <NUM>. The connector of the cable under test is then installed in the receptacle of the datacomm SFP.

With additional reference to <FIG>, the VFL <NUM> is shown installed in an SFP port of a portable host <NUM>. A cable under test <NUM> is connected to the receptacle <NUM> of the VFL <NUM>. The portable host <NUM> may include replaceable and/or rechargeable batteries that serve as a power source for the VFL <NUM>. The portable host <NUM> allows the VFL <NUM> to be used in situations where a cable under test <NUM> is not in a location where compatible ports to support operation of the VFL <NUM> are available.

In one embodiment, the VFL <NUM> may communicatively interface with another device from which operational control over the VFL <NUM> is made. For instance, a mobile phone, a tablet or a computer may interface with the VFL <NUM> by way of a wired connection, by way of a wireless connection (e.g., a Bluetooth connection or a WiFi network connection), or by way of the host <NUM> and interface <NUM>. The user may interact with control software executed by the other device (e.g., the mobile phone, tablet or computer) to control operation of the VFL <NUM>, such as remotely commanding the VFL <NUM> to turn the light source <NUM> on or off, or any of the other control operations mentioned herein. This control may be carried out instead of or in addition to control operations made using the user input <NUM>. In one embodiment, the user input <NUM> may be omitted. In these embodiments, the VFL <NUM> may be controlled remotely by the operator, such as a position in a data center but out of arm's length from the VFL <NUM>. For instance, while inspecting the length of the cable under test, the operator may issue control commands to the VFL <NUM> via a portable electronic device (e.g., a mobile telephone).

In the case where control is made by way of communications through the host <NUM> and interface <NUM>, the VFL <NUM> and host <NUM> may engage in the exchange of control signals. In the embodiment where the VFL <NUM> and the port of the host <NUM> are made in accordance with the MSA SFF standard, the control signals may be in the form of MSA diagnostic messages using, for example, vendor assignable data bytes.

In another embodiment, the VFL <NUM> communicates wirelessly with the device that executes the control software. In this case, the VFL <NUM> has an appropriate wireless interface. The wireless interface may have an antenna that extends out of the housing of the VFL <NUM> to reduce shielding that the housing may have on signal propagation. For instance, the antenna may be located next to or in place of the user input <NUM>. In one embodiment, the antenna may be located in a cover that also serves as the user input <NUM>. For instance, the cover may form part of a push button or a rotary dial switch.

A physical user input <NUM> as described in connection with the VFL <NUM> may be added to a data communications SFP device. In this embodiment, the user input may be used to control a dedicated function of the data communications device. For instance, many data communications SFP devices are capable of demodulating optical signals at multiple wavelengths. The user input may be used to scroll through the wavelengths. An output (e.g., an LED or MSA data event) may signal to the operator that an input data signal is present at the currently selected wavelength. In another embodiment, the user input may be used to change a data transmit wavelength.

Claim 1:
A visual fault locator (<NUM>), comprising:
a housing (<NUM>);
a receptacle (<NUM>) retained by the housing and configured to retain a connector of a fiber optic cable under test;
a light source (<NUM>) retained by the housing and positioned relative to the receptacle to emit light into a core of the fiber optic cable under test, wherein the emitted light is configured to detect a break in the core of the fiber optic cable under test by being visually detectable through a jacket of the fiber optic cable under test at a point of a break in the core; and
wherein the housing is physically configured so as to be removably installed in a port of a host device (<NUM>), an interface (<NUM>) in the form of an electrical connector retained by the housing, the interface (<NUM>) mates with a corresponding connector of the host device (<NUM>) the visual fault locator not including a power source and receiving operational power for the light source from the host device via the interface, characterized in that the visual fault locator comprises a control circuit (<NUM>) that controls operation of the light source, the control circuit is powered by the operational power from the host device via the interface, the visual fault locator further comprises a physical user input (<NUM>) retained by the housing and operable by a user to control the control circuit to change operating states of the light source, and the visual fault locator is not capable of transmitting communications data in an optical signal.