Category Archives: Optical Splitter

Typical example of photonic packaging

The passive optical power splitter is one of the key elements in a passive optical network (PON), which equally splits the signal power from the optical line terminal (OLT) in the central office (CO) to each optical network unit (ONU). It can branche and couple waves without converting optical transmissions into electric signals, for connecting households to thlecommunication carriers in optical communication networks. Planar lightwave circuits (PLC Splitter) can provide various key practical devices for such optical networks because of their suitability for large-scale integration, long-term stability, and mass production capability. In order to utilize the integration capability of PLC devices, the input and output fibers have to be connected to the PLCs. The fiber connected splitters are required to exhibit not only htgh optical performance (such as low loss, wavelength flatness and low polarization dependence) but also long-term reliability. However, to attain a reliable low loss splitter, connection methods must be precise and meticulous.

Figures1 a and b show typical schematic configurations of an unpackaged and a packaged PLC-type optical splitter, respectively. The unpackaged 1×8 PLC Optical Splitter includes a PLC (splitter) chip, and single-channel (input) and eight-channels (output) fiber arrays. The three parts are mounted by an adhesive, as shown in Fig 1a. However, in a packaged device, the mounted optical splitter is secured in its housing by applying fixing adhesive between the Al fixing blocks and the fibers. Moreover, an adhesive is used to bond the rubber boots and the end of fiber arrays in the housing, as shown in Fig1b. It is very clear that different types of adhesive are nedded for bonding different parts of the PLC package. In fact, a large number of different materials are ultimately required for assembling the splitter packages. Table 1 shows the physical properties of materials used in an adhesive-based optical splitter package. Shows the appearance of a bonded PLC optical splitter package in an aluminum package.



Figures 1    (a)Schematic configuration of unpackaged PLC optical splitter.

                          (b) Schematic configuration of packaged PLC optical splitter.


Table 1

Physical properties of materials used in adhesive-based packaging of an Optical Splitter


Continue reading

Introduction To Fiber Optic Couplers

A fiber optic coupler is a device used in fiber optic systems with single or more input fibers and single or several output fibers, which is different from WDM  devices. WDM multiplexer and demultiplexer divide the different wavelength fiber light into different channels, while fiber optic couplers divide the light power and send it to different channel.

Most types of couplers work only in a limited range of wavelength (a limited bandwidth), since the coupling strength is wavelength-dependent (and often also polarization-dependent). This is a typical property of those couplers where the coupling occurs over a certain length. Typical bandwidths of fused couplers are a few tens of nanometers. In high-power fiber lasers and amplifiers, multimode fiber couplers are often used for combining the radiation of several laser diodes and sending them into inner cladding of the active fiber.

A basic fiber optic coupler has N input ports and M output ports. N and M typically range from 1 to 64. M is the number of input ports (one or more). N is the number of output ports and is always equal to or greater than M. The number of input ports and output ports vary depending on the intended application for the coupler.

Light from an input fiber can appear at one or more outputs, with the power distribution potentially depending on the wavelength and polarization. Such couplers can be fabricated in different ways:
Some couplers use side-polished fibers, providing access to the fiber core;
Couplers can also be made from bulk optics, for example in the form of microlenses and beam splitters, which can be coupled to fibers (“fiber pig-tailed”).

Fiber optic couplers can either be passive or active devices. Passive fiber optic couplers are simple fiber optic components that are used to redirect light waves. Passive couplers either use micro-lenses, graded-refractive-index (GRIN) rods and beam splitters, optical mixers, or splice and fuse the core of the optical fibers together. Active fiber optic couplers require an external power source. They receive input signals, and then use a combination of fiber optic detectors, optical-to-electrical converters, and light sources to transmit fiber optic signals.

Types of fiber optic couplers include optical splitters, optical combiners, X couplers, star couplers, and tree couplers. The device allows the transmission of light waves through multiple paths.

Fused couplers are used to split optical signals between two fibers, or to combine optical signals from two fibers into one fiber. They are constructed by fusing and tapering two fibers together. This method provides a simple, rugged, and compact method of splitting and combining optical signals. Typical excess losses are as low as 0.2dB, while splitting ratios are accurate to within ±5 percent at the design wavelength. The devices are bi-directional, and offer low backreflection. The technique is best suited to singlemode and multimode couplers.

Choices for fiber optic coupler also include Single window narrow band, Single window Wide band, and Dual window Wide band fiber optic coupler. Single window fiber optic coupler is with one working wavelength. Dual window fiber optic coupler is with two working wavelength. For Single mode fiber, is optimized for 1310 nm and 1550 nm; For Multimode fiber, is optimized for 850 nm and 1310 nm.

High Density Fiber Patch Cables For Using In Data Center

Data center fiber optical transmission system requirements on the bandwidth shows high growth trend, while the use of a new generation of fiber optic and fiber optical module can continue to explore the potential of optical network bandwidth. Since multi-mode fiber has lower overall cost of active and passive, prompting multimode fiber applications have an absolute advantage in the data center. The launch of OM4 new category EIA/TIA492AAAD multimode fiber standard, providing a better transmission way for multi-mode fiber widely used in the future. Multimode fiber from OM1 to OM2, from OM3 cable use VCSEL laser optimization technique to OM4 cable, the bandwidth is progressively enhanced, promoted by a large growth requirements of online media and application in the cloud computing environment, this module is the ideal communication solution for data center, server farms, network switches, telecom switching centers and many other needs high-speed data transmission embedded applications, the system applications include data aggregation, backplane communications, proprietary protocol data transmission and other high-density / high-bandwidth applications.

In the 40G/100G state port device such as QSFP will be directly connected to the MTP/MPO connector, regardless if the fiber channel is connected by several fiber optic cables, or what type of connection of the fiber connected. 40G/100G of equipment and equipment ultimately channel connection need to form a special model, so that the equipment transmitting end and the receiving end of the channel correspond to each other.

MPO / MTP high density fiber pre connection system currently mainly used in three areas: high-density data center environment applications, fiber-to-building applications, inside connection applications between optical splitter, 40G, 100G QSFP SFP+ and other fiber optical transceiver devices. There are a series of high-density parallel optical connectivity products adaptable to modern data center fiber transmission, which are 16��8 OM3/OM4 MPO bundle, MPO Loopback and QSFP Jumper.

MPO/MTP Fiber Cable is offered for various applications for all networking and device needs like 100 Gigabit modules. It uses a high-density multi-fiber connector system built around precision molded MT ferrule. MPO/MTP fiber cable is available in UPC and APC finishes, and support both multimode and single mode applications. Work with both VCSEL laser and LED sources, 10G OM3 OM4 MPO/MTP Cable provide 10 gigabit data transfer speeds in high bandwidth applications and they are 5 times faster than standard 50um fiber cable. Multimode MPO/MTP Cable is the cable of choice for most common local fiber systems as the devices for multimode are far cheaper. Single-mode MPO/MTP Cable is primarily used for applications involving extensive distances. The MPO/MTP Trunk cable is designs for Data Center Applications. The single-mode and multimode MPO/MTP cables are round cables with the outer diameter of 3.0 mm or 4.5 mm. The connector the cable is terminated on is so called MPO/MTP connector.

With server virtualization and cloud computing development and the trend of network integration, bringing greater demand of faster and more efficiently data center networks. Currently 10G switch is consist of 48 10G channels per line card, mainly limited by the SFP+ module form factor. To meet the higher bandwidth requirements, customers can use the higher-density QSFP+ ports developed by QSFP+ Jumper, and by increasing the per-channel rate and increasing port density to achieve customers’ high bandwidth requirements.

Common Passive Fiber Optical Splitters

Fiber optical splitter, also named fiber optic coupler or beam splitter, is a device that can distribute the optical signal (or power) from one fiber among two or more fibers. Fiber optic splitter is different from WDM(Wavelength Division Multiplexing) technology. WDM can divide the different wavelength fiber optic light into different channels, but fiber optic splitter divide the light power and send it to different channels.

Work Theory Of Optical Splitters

The Optical Splitters “split” the input optical signal received by it between two optical outputs, simultaneously, in a pre-specified ratio 90:10 or 80:20. The most common type of fiber-optic splitter splits the output evenly, with half the signal going to one leg of the output and half going to the other. It is possible to get splitters that use a different split ratio, putting a larger amount of the signal to one side of the splitter than the other. Splitters are identified with a number that represents the signal division, such as 50/50 if the split is even, or 80/20 if 80% of the signal goes to one side and only 20% to the other.

Some types of the fiber-optic splitter are actually able to work in either direction. This means that if the device is installed in one way, it acts as a splitter and divides the incoming signal into two parts, sending out two separate outputs. If it is installed in reverse, it acts as a coupler, taking two incoming signals and combing them into a single output. Not every fiber-optic splitter can be used this way, but those that can are labeled as reversible or as coupler/splitters.

Attenuation Of Fiber Optic Splitter

An interesting fact is that attenuation of light through an optical splitter is symmetrical. It is identical in both directions. Whether a splitter is combining light in the upstream direction or dividing light in the downstream direction, it still introduces the same attenuation to an optical input signal (a little more than 3 dB for each 1:2 split). Fiber optic splitters attenuate the signal much more than a fiber optic connector or splice because the input signal is divided among the output ports. For example, with a 1 X 2 fiber optic coupler, each output is less than one-half the power of the input signal (over a 3 dB loss).

Passive And Active Splitters

Fiber optic splitters can be divided into active and passive devices. The difference between active and passive couplers is that a passive coupler redistributes the optical signal without optical-to-electrical conversion. Active couplers are electronic devices that split or combine the signal electrically and use fiber optic detectors and sources for input and output.

Passive splitters play an important position in Fiber to the Home (FTTH) networks by permitting a single PON (Passive Optical Network) network interface to be shared amongst many subscribers. Splitters include no electronics and use no power. They’re the community parts that put the passive in Passive Optical Network and are available in a wide range of break up ratios, including 1:8, 1:16, and 1:32.

Optical splitters are available in configurations from 1×2 to 1×64, such as 1:8, 1:16, and 1:32. There are two basic technologies for building passive optical network splitters: Fused Biconical Taper (FBT) and Planar Lightwave Circuit (PLC). FBT Coupler is the older technology and generally introduces more loss than the newer PLC Splitter.