Data Center Fiber Solution

You Yuan Optic Communication: a First-Class Data Center Fiber Solutions Manufacturer

Shenzhen You Yuan Communication is passionate working on Telecommunication industry for 20 years, mainly offering passive fiber optic materials and major focus on Last Mile FTTX and FTTR Networks.

Variety of Products

We can provide customers with indoor/outdoor optical cables, patch cords, FBT couplers, PLC splitters, optical fiber wall sockets, MPO rack-mounted optical fiber distribution frames, optical fiber access terminal boxes, optical fiber adapters, optical fiber attenuators and other optical fiber communications products and accessories.

Advanced Production Equipment

Our 10,000 square meter factory is equipped with advanced optical cable manufacturing equipment and inspection and testing equipment. These include optical fiber geometric parameter testers, laser calipers, optical amplifiers, horizontal tensile testing machines, high and low temperature test chambers, long test benches, water penetration testing devices, etc.

Rich Market Experience

Our fiber optic products and optical accessories are sold all over the world, such as Africa, Southeast Asia, America and other regions. Our mission is to provide customers with high-quality products and services at the right time and at the right price to help them increase their market share.

Multiple International Certifications

Our company has obtained ISO 9001, CE, ROHS, CPR and other international certifications. Our advanced management, strict quality control and product testing strength create world-class production specifications and features while maintaining competitive prices.

8F MPO Singlemode Fiber Patchcord
As data center demands continue to surge, the importance of high-density and efficient connectivity solutions cannot be overstated. The transition from traditional connectors to advanced MPO...
read more
8F MPO OM3 Fiber Patchcord
The landscape of fiber optic connectors is undergoing a transformative shift, with traditional connectors like MTRJ and E2000 being upgraded to the more advanced MPO (Multi-fiber Push-On) connectors.
read more
8F MPO OM4 Fiber Patchcord
The OM4 8-core MPO trunk fiber patchcord is a specialized optical fiber cable meticulously designed to meet the stringent demands of high-density data center and enterprise network applications....
read more
8F MPO OM5 Fiber Patchcord
The OM5 8F MPO Fiber Patchcord represents a significant advancement in optical connectivity. Designed for superior performance in high-speed, high-bandwidth environments, these patchcords offer...
read more
12F MPO Singlemode Fiber Patchcord
The Single-mode 12-core MPO trunk fiber patchcord represents a pinnacle in specialized optical fiber cables, meticulously engineered to cater to the exacting needs of high-density data center and...
read more
12F MPO OM3 Fiber Patchcord
You Yuan's extensive range of MPO backbone jumpers offers versatile solutions for data center computer room wiring. These MPO jumpers play a crucial role in optimizing connectivity within data...
read more
12F MPO OM4 Fiber Patchcord
Data centers are continually striving for more efficient use of space and resources. The 12F MPO OM4 Fiber Patchcord is designed with this in mind. It provides a high-density solution for data...
read more
12F MPO OM5 Fiber Patchcord
You Yuan's comprehensive range of MPO backbone jumpers is designed to cater to the specific needs of data center computer room wiring. These MPO jumpers offer an efficient and cost-effective...
read more
8F MPO To LC Singlemode Fiber Patchcord
You Yuan offers a diverse range of MPO branch jumpers tailored to meet the specific requirements of data center computer room wiring. These MPO breakout cables provide a cost-effective and...
read more
8F MPO To LC OM3 Fiber Patchcord
YouYuan's MPO Patch Cables have been carefully engineered to support high-density fiber interconnects, making them an ideal choice for data centers that prioritize space-saving and efficient cable...
read more
8F MPO To LC OM4 Fiber Patchcord
The future of data connectivity is bright, and with YouYuan's MPO Patch Cables as part of your network infrastructure, you can embrace this future with ease, efficiency, and performance. Whether...
read more
8F MPO To LC MPO OM5 Fiber Patchcord
In the fast-paced world of modern communication technology, data centers are the beating heart of our digital landscape. The insatiable demand for data transmission and processing requires data...
read more

First 12 Last

As data center demands continue to surge, the importance of high-density and efficient connectivity solutions cannot be overstated. The transition from traditional connectors to advanced MPO connectors, such as 8F MPO Singlemode Fiber Patchcords, is a pivotal step in addressing the challenges posed by modern data center requirements.

Brief Introduction to Data Center Fiber Solutions

Data center networks are critical components of modern IT infrastructure, enabling organizations to process and store vast amounts of data. As the volume of data handled by these networks continues to grow, there is an ever-increasing need for flexibility and connectivity between servers and switches throughout the data center. Data center fiber solutions integrate fiber optic patch cords, fiber optic adapters, fiber optic connectors and other products. Their function is to ensure that the data center can achieve greater flexibility to connect various devices while ensuring the stability of the connection.

Common Types of Data Center Fiber Solutions

Fiber Patch Cords Types

Fiber patch cord (Fiber Patch Cable or Fiber jumper) are used for linking the equipment and components in the fiber optic network, is a fiber cable that has fiber connectors installed on one or both ends. Fiber optic patch cords are designed and polished to different shapes to minimize back reflection. This is particularly important in single mode applications.

According to the Mode
Single-Mode Fiber Patch Cords: Generally yellow, the connector and protective sleeve are blue, and the transmission distance is long.
Multimode Fiber Patch Cords: Generally orange or aqua blue, the connector and protective sleeve are beige or black, and the transmission distance is short.

According to the Connector Type
FC Fiber Patch Cord: FC fiber patch cord is one of the most common connection devices in single-mode networks. Its external reinforcement method is a metal sleeve, and the fastening method is a turnbuckle. It is common on the ODF side (the most common on the patch panel). FC connectors are generally used in telecommunications networks. Its advantages are that they are reliable and dust-proof. The disadvantage is that the installation time is slightly longer.
ST Fiber Patch Cord: ST fiber patch cord is the most common connection device in multimode networks, and it is also the most common connector type in Base10 fiber optic connections. It is commonly used in fiber optic distribution frames. The shell is round, fastened with turnbuckles, and the core is exposed. This type of fiber optic patch cord needs to be inserted first and then rotated half a turn to secure the bayonet.
SC Fiber Patch Cord: SC fiber patch cord is a TIA-568-A standardized connector. It was not widely used in the initial stage due to its high price. Later, it was gradually used in connection with GBIC optical modules due to its excellent performance. Commonly found on routers and switches, its casing is rectangular, and the fastening method is a plug-and-pull type. Unlike ST/FC, it does not need to be rotated.
LC Fiber Patch Cords: LC fiber patch cords are usually connected to SFP optical modules. The connector is similar to the SC connector, but smaller than the SC connector. The size of its pin and the sleeve is 1.25mm, which is half of the ordinary SC and FC. Its advantages are good performance , and to a certain extent, it can increase the density of optical fiber connectors in the optical fiber distribution frame, and it is a very good single-mode fiber patch cord.

According to the Application
MTP/MPO Fiber Patch Cords: This type of fiber optic patch cord is often used in fiber optic line environments that require high-density integration during the wiring process. The advantage is a simple push-pull locking structure for easy installation and removal. Therefore, its installation is very time- and cost-saving.
Armored Fiber Patch Cords: Armored fiber optic patch cords are commonly found in computer rooms and are suitable for harsh environments. Its advantage is that it can be moisture-proof and fire-proof without using a protective cover, and has anti-static properties and acid and alkali resistance. This type of fiber optic patch cord can also save space and reduce construction costs.
Conventional Fiber Patch Cords: Conventional fiber optic patch cords include OS2 single-mode simplex, OM4 multi-mode, OM3 multi-mode, OM2 multi-mode, OM1 multi-mode, OS2 single-mode simplex, and OM5 multi-mode. Among them, OM5 optical fiber jumper is currently the most popular product. It has an aqua sheath and is often used in higher bandwidth applications. It has strong scalability, compatibility and interoperability, which can effectively reduce costs.

According to the Polishing Types
To reduce back reflection, fiber optic connections are constructed and polished into a variety of shapes. -30dB, -40dB, -50dB, and -60dB are typical back reflection grades.
PC (Physical Contact): For single-mode and multimode applications, the typical back reflection is -40dB.
Ultra Physical Contact (UPC): For single-mode applications, the typical back reflection is -50dB.
APC (Angled Physical Contact): For single-mode applications, the typical back reflection is -60dB.

Fiber Connectors Types

A fiber connector is also referred to as a “termination” and enables you to quickly connect/disconnect the fiber cables. Many fiber connector types have a spring-loaded connection to ensure that there is a constant force that is mating the two fibers together to confirm that you have a good clean connection for the pulse to go through. These spring-loaded connections also pull their weight by eliminating any air gaps between the connectors. An air gap will quickly rob the light transmission of making its way from fiber to fiber.

ST Fiber Connector

These connectors use a 2.5mm ferrule that is mounted on the inside of the housing. This is an older style connector but is still commonly used in multimode applications. The ST connector, while older, is still commonly in use in today’s fiber installations due to it being extremely easy to install and its relatively low cost compared to some other connectors. This connector has a keyed “slot” on the end of the connector that helps keep it tightly mated to the fibers and in alignment when they are decoupled and recoupled.

SC Fiber Connector

The SC connector was invented to directly replace the ST connectors and, as a result, has become one of the most common fiber connectors in the world. Similar to the ST connector, this SC style also utilizes a 2.5mm ferrule. The SC connector is what is called a non-optical disconnect connector. This term means that once the connector has been installed, any pushing or pulling on the jacket of the cable will not cause the ferrule to disconnect, which is a prevalent problem with the ST model connectors. This ensures that the signal is not to be interrupted. Sometimes with the ST connectors, when they are pulled back, the spring mechanism will slam the fibers together. An SC connector can alleviate these problems. SC connectors are perfectly suited for datacoms and telecoms.

FC Fiber Connector

The FC connector also utilizes a 2.5mm ferrule. This connector shares a round profile like the ST connectors we reviewed but instead of coming equipped with a spring-loaded twist lock mechanism, this connector has a threaded connection. Like the SC connector, the FC connector also has a non-optical disconnect advantage. Because this connector threads onto a connection, you can be sure that this connector will stay stable and mated to its connection, even during rougher environments.

LC Fiber Connector

LC Connectors are a member of what is referred to as the small form factor (SFF) line of connectors. These SFF connectors were initially invented to fill a need for large fiber count applications. In some installations there are dozens of connectors being plugged in and these connectors make life much easier. The LC connector uses a 1.2mm ferrule and has about half the footprint size of the other connectors. It does share the same non optical disconnect as the SC and FC share. LC connectors can quickly be terminated and have a couple different methods to achieve that. The SFF design makes this the perfect connection for a high-density application, which is why this is the connection of choice for networking and transceivers.

MTP/MPO Fiber Connector

These connectors are used for ribbon cable. In single mode use these will typically get about 0.25dB loss and about 0.20dB loss in multi-mode. These are also available in the smaller 8 fiber connectors in this configuration. Single mode ferrules are angled at 8°. This is mostly used in very high-density applications with ribbon cable to reduce the connector space that may be required. MPO/MTP connectors combine 8, 12 or 24 fibers into one single and compact interface. They can put this amount of cable in the same space an SC connector would take up. This very effectively saves rack space on a high-density rack.

Fiber Adapters Types

Fiber optic adapters, also known as couplers, are essential components within fiber optic networks. They serve as interfaces for connecting fiber optic cables, facilitating the transmission of light signals between two separate fiber optic lines. They are very essential optical fiber connection components, widely applied in local area networks (LANs), optical fiber communication systems, and FTTH (Fiber to the Home). Adapters are very important connecting components used to accurately terminate the optical fiber cables or fiber connectors.

LC to LC Fiber Optic Adapter

LC to LC fiber optic adapter is a type of fiber optic adapter, which is used to provide cable to cable or cable to equipment fiber optic connection. This adapter can be used to connect two LC fiber cables and it is complaint with international standards, making them compatible within a wide range of fiber optic application. LC to LC fiber optic adapter is available for single-mode and multimode versions. Commonly used types of single-mode LC to LC fiber optic adapter include LC/APC to LC/APC and LC/UPC to LC/UPC fiber optic adapter, while the multimode one only has LC/UPC to LC UPC fiber optic adapter. And there are simplex and duplex type.

LC to SC fiber Optic Adapter

LC to SC fiber optic adapter is a type of fiber optic adapter, that is used to connect cable to cable or cable to other equipment. This fiber optic adapter fits two different kinds of connectors, LC and SC, so, it is also called hybrid fiber optic adapter. And this adapter is suited for both single-mode and multimode applications. Most of this fiber optic adapter are plastic, but some of them can be metal. Besides it is possible to divide LC to SC fiber optic adapter into different versions of female to male and male to female hybrid fiber optic adapter.

MPO Fiber Optic Adapter

MPO fiber optic adapter, also called MPO fiber optic coupler, is designed with two female connections on both ends to provide two MPO patch cable connection This adapter has an adjustable keyway which allows it to change keyway orientation between Key-up to Key-down for straight wiring or Key-up to Key-up for cross wiring applications. A MPO adapter has protective caps that can prevent dust and debris from entering. And MPO adapter is suitable for both single-mode and multimode. This adapter is used in high-density backplane and printed circuit boar (PCB) applications in data and telecommunications systems.

Data Center Fiber Solutions Technical Parameters

productcate-1200-552

Multimode Or Singlemode: Which Fiber Type is Best in the Data Center?

Today, data center technicians largely have two high-level options when it comes to selecting fiber types. Multimode fiber, and singlemode fiber. The following content will help you choose between the two.

Benefits of Multimode Fiber in the Data Center

Multimode Fiber (MMF) is still firmly the front runner in modern Enterprise Data Centers. A key benefit of using multimode fiber is that it is a low cost way to transport high data rates over relatively shorter or smaller distances. Multimode fiber has evolved from being optimized for multimegabit-per-second transmission, using light-emitting diode (LED) light sources, to being optimized to support multigigabit transmission using 850nm vertical cavity surface emitting laser (VCSEL) sources - which tend to be more affordable than their singlemode counterparts.

This advancement in performance is clear, due to the classifications assigned to MMF by the standards bodies. OM1 and OM2 represented the earlier MMF types with low modal bandwidth and very limited support for higher speed optics. OM3 and OM4 represent the newer, laser-optimized MMFs that are typically installed in modern data centers today.

Benefits of Singlemode Fiber in the Data Center

Singlemode fiber (SMF), which is designed with a much smaller core, is the sensible and most realistic choice for longer-reach applications in the data center, such as extended runs in the fabric between leaf and spine switches, spine and routers, and into the transport network to connect data centers in different locations. With a higher bandwidth, SMF does not have the modal dispersion limitations inherent in MMF.

Therefore, SMF is used in applications where support for higher and next-generation bandwidths can absolutely be guaranteed. This means that SMF is a good choice for hyperscale and service provider data center owners to deploy, as it supports longer distances. Large data centers and hyperscale data centers usually deploy SMF to connect multiple halls and extended equipment zones using a centralized cross-connects architecture at the MDA. They also typically employ a dedicated optical distribution frame (ODF). By deploying an ODF, technicians can make sure that cables are sustained at an optimum length for transmission, whilst other data halls and equipment zones can be efficiently patched to one another with minimum disruption to service and networking equipment.

Fiber Connectors As the Final Consideration

Clearly both MMF and SMF have their advantages and disadvantages - which option a data center designer chooses, will depend on a range of factors from budget to use case and more. However, data center designers should also consider the use and choice of fiber connectors as part of a fiber selection process. Having evolved alongside fiber-optic cabling, driven by increasing fiber density, fiber connectors work to pull the whole system together. In the early 2000s the duplex LC connector emerged as the predominant two-fiber type, and remains so today.

While the evolution of the duplex connector was underway, array connectors (parallel optics) were also progressing. The multifiber push-on (MPO), which was first deployed in public networks, had become a firm first choice for rapidly deploying cabling into data centers. Finally due to its compact size, the MPO allows 12 or more fibers to be terminated in a compact plug, occupying the same space as a duplex LC. The MPO’s high density enables installation of preterminated, high-strand-count cables, while eliminating the time-consuming process of field installing connectors on site.

Ultimate Guide

Q: What is a data center?

A: A data center is a building or portion of a building whose primary function is to house a computer room and its support areas.

Q: How do you calculate upstream & downstream bandwith per user on an ONT? What is your general recommendations on planning for bandwidth in terms of the number of ONTs I am going to need?

A: ONT itself is going to be very high performance connected to fiber, so it itself is high performance, and often times can have multiple ports connecting to different devices. Most ONTs offer either four ports or eight ports, depending on how many devices you’re going to hook up. So if you’re going to hook up to a lot of wireless access points that consume a lot of bandwidth, that would be a consideration. One of the things you can do from the ONTs is dynamic bandwidth allocation. This allows you to go into each ONT and each port and allocate a certain amount of bandwidth guaranteed per port, and then you can also have the ability to burst, too. So it really depends on the different bandwidth requirements of the devices that are going to plug into the ONT.

Q: Does an ONT need to be in an enclosure?

A: In a POL, the Optical Network Terminal (ONT) is can be wall mounted or ceiling mounted. The do not need to be an enclosure unless they are in a place where they might be accessed by the public - say, in a hotel or an MDU. In that case, they would likely be put in an in-wall enclosure.

Q: Are there any special requirements for the optical fiber used in passive optical LAN?

A: Each ONT end device just requires one strand of single mode fiber. And the connectors typically used in passive optical LAN are SC/APC angle polish connectors. Note: some manufacturers now offer a way to leverage multimode fiber in applications where the fiber plant was already installed.

Q: Are there any special requirements for the optical fiber used in passive optical LANs?

A: In a Passive Optical LAN each ONT end device requires one strand of single-mode fiber. The connectors typically used in passive optical LAN are SC/APC angle polish connectors on the end. If you have existing single mode in your backbone, then you’re halfway there.

Q: How do I plug an MPO connector into my OTDR?

A: Many OTDRs have only one plug connector, which can make plugging in your MPO confusing. Luckily, there are different ways to connect your OTDR to the MPO connector. If you want to see the MPO connector, you’re going to need a launch fiber. That launch fiber is going to need to have the same MPO connector. If you’re doing 12 fiber, you need a 12 fiber MPO launch. And if you’re doing 24 fiber MPO, you’re going to need a 24 fiber MPO launch cable. The length of that cable is going to be a function of the distance of the fiber you’re testing, or the pulse widths that you’re using. If you’re using a short pulse width, a three or a five nanosecond, maybe a 10 nanosecond pulse width, you can get by with a pretty short launch fiber. Longer the better, but say at least 20 or 30 meters. Now on the OTDR end of that launch fiber, you could either have it be a fan out cable, or you can put a cassette there and move through the ports of the cassette. Also, there are manufacturers who make a switch. The switch has say an SC port and inside the switch it will move between 12 or 24.

Q: Which MPO connector should I use?

A: The three most common MPO connector options are MPO-8, MPO-12 and MPO-24. MPO-8 is a legacy standard for the QSFPs, coming out of the transceivers running 40 Gigabit or 100 Gigabits. It is used for both multimode and singlemode transceivers and breakouts, but offers the lowest density option, because you’ll have to have more components for the MPO-8 as you move forward into higher speeds. The MPO-12 is the legacy embedded base and with the use of different modules and array fanouts can accommodate multiple configurations. MPO-24 is the newest option and is used on the trunk cables and modules. MPO-24 helps to future proof your network because it provides the highest panel density, allows you to use fewer components and may offer the lowest first installed cost. MPO 24 trunk implementations provide significant advantages for duplex and parallel implementations, providing for faster installation and better pathway efficiency.

Q: What’s the difference between PON, G-PON, and NG-PON?

A: PON is the general concept of Passive Optical Networking, which refers to the use of splitter typologies in point to multipoint technologies where one fiber is split out to multiple endpoints. GPON is the 2.5 Gbps Passive Optical Network, while NG-PON is in general, everything which is Next Generation, meaning 10 Gbps and beyond. In the standards they talk about Next Gen PON1, which is then the 10 Gbps variants, and Next Gen PON2, which are then the TWDM PON,

Q: What is the number one cause of network failure?

A: The leading cause of network failures is dirty connections. Almost all the time, the dirt is completely invisible to the naked eye, but since the diameter of a fiber core is so small (50 microns for multimode fiber and only 8 microns for singlemode fiber) it doesn’t take much to block the light on the fiber endface. When the dust cap is removed the ferrule end face can easily be contaminated by direct contact with skin oil, grease, salt, fingerprints, lint, uncured epoxy, grime or dust. Even just open air exposure may result in moisture and dust sticking to the end-face. When the dust caps are off your connectors are at risk of contamination. This is why proper inspection and cleaning techniques are so important, especially with today’s tight loss budgets where too much loss from a dirty connection can have a direct impact on bit error rate, insertion loss and optical return loss which will impact system performance and reliability.

Q: Does a Passive Optical LAN (POL) use multimode or single-mode fiber?

A: Passive optical LAN (POL) architectures primarily use single-mode fiber because of the medium’s high capacity and ability to support long link lengths - up to 20 km. In a POL architecture. In a POL, a passive single-mode fiber network runs down to the desktop, through an optical splitter and into a thin-client edge device or Optical Network Terminal (ONT). Recently single-mode to multimode optical splitters have been introduced that enable cost-effective re-use of existing multimode fiber cabling for Passive Optical LANs inside buildings and across a campus.

Q: What is polarity? And why is it important?

A: Polarity defines direction of flow, such as the direction of a magnetic field or an electrical current. In fiber optics, it defines the direction that light signals travels through an optical fiber. To properly send data via light signals, a fiber optic link’s transmit signal (Tx) at one end of the cable must match the corresponding receiver (Rx) at the other end. In duplex fiber applications, such as 10 Gig, data transmission is bidirectional over two fibers where each fiber connects the transmitter on one end and to the receiver on the other end. The role of polarity is to make sure that this connection is maintained. Polarity in multi-fiber MPO type cables and connectors is more complicated. Industry standards call out three different polarity methods for MPOs - Method A, Method B and Method C. And each method uses different types of MPO cables.

Q: What fiber is typically being used with the 200 400 Gig circuits?

A: Most likely you are looking at either OM4 or OM5 multimode fibers. Of course single mode will always be an option, but on the multimode side you have OM5 fiber, which is optimized for the short wave division multiplexing (SWDM) so depending on the distances you need to support, those to fiber types will give you the most cost effective solution.

Q: How do you inspect and clean an unpinned MPO connector?

A: An unpinned MPO is inspected in the same way as a pinned MPO, however from an inspection perspective there’s no contact made with the fiber. You’d use the same inspection probes that will find the fibers, inspect them, and do a pass fail analysis. For cleaning, you can use the cassette style cleaners. In fact in some ways they are easier to clean than a pinned connector.

Q: What is Wavelength Division Multiplexing (WDM) Technology?

A: Wavelength division multiplexing (WDM) allows multiple wavelengths, typically 2 or 4 wavelengths over a single fiber. The IEEE 802.3bs 200 Gb/s & 400 Gb/s Ethernet Task Force in 2016 added 200 Gb/s capability to support a cost and performance optimized migration path to 400 Gb/s that includes support for 200 Gb/s with at least 2 km of SMF (4l WDM duplex fiber) and at least 10 km of SMF (4 l WDM duplex fiber).

Q: What types of connectors are used in Data Center applications?

A: In fiber optic systems for data centers, LC, SC and MPO optical fiber connectors are often used.

SC (square connector) connectors have a push-pull coupling end face with a spring-loaded ceramic ferrule, and is ideal in data center applications.

LC (Lucent connector) connectors - also push-pull connectors - came along after SC connectors, and feature a smaller ferrule (for this reason, it’s known as a “small form-factor connector”). Its smaller size makes it ideal for dense data center racks and panels.

MPO connectors are used for ribbon cables with anywhere from eight to 24 fibers.

Q: What type of fiber do you recommend for data center applications?

A: To support the high bandwidths required in data centers, most companies are installing at least OM4, laser optimized multimode fiber. Some companies are installing single-mode fiber, but that requires more expensive optics. A new option that is emerging is OM5, a wide bandwidth multimode fiber which allows short wavelength division multiplexing. This means the fiber can carry multiple wavelengths of light over the same fiber, increasing bandwidth significantly and yet still allowing the use of lower cost multimode optics.

Q: Should I install singlemode or multimode fiber in my network?

A: While some people choose to install singlemode fiber because of it’s high bandwidth, multimode fiber continues to be a popular choice for enterprise applications. Newer grades of multimode fiber, such as OM4 laser optimized fiber and OM5, wideband multimode fiber, have the bandwidth to support most applications over the distances required, plus the cost for the optics remains lower than the cost of singlemode optics.

As one of the most professional data center fiber solution suppliers in China, we're featured by quality products and low price. Please rest assured to wholesale or buy discount data center fiber solution for sale here and get quotation from our factory. Also, customized service is available.

MPO Fiber Patchcord, LC Duplex Fiber Patchcord, 1F FTTH Drop Cable