A comprehensive understanding of fiber to home FTTH and optical splitter

What is fiber to the home FTTH？

Fiber to home English is FTTH（Fiber to the home）, It is a transmission mode of optical fiber communication . As the name suggests, the optical fiber is directly connected to the user terminal .FTTH yes FTTx An access method in , What is FTTx？

FTTX It is a general term for various application types of broadband optical access network ,“X” There are many variations , It can be optical fiber to the building (FTTB)、 Optical fiber to junction box (FTTCab)、 Fiber to the side of the road (FTTC)、 Fiber to desktop (FTTD)、 Fiber to home (FTTH)、 Fiber to station (FTTP)、 Optical fiber to the office (FTTO)、 Fiber to user (FTTu) etc. .

FTTx The technical scope ranges from the office end equipment in the regional telecommunication room to the user terminal equipment , Including optical line terminals OLT（Optical Line Terminal）, Optical network unit ONU（Optical Network Unit）, Optical network terminal ONT（Optical Network Terminal）.

A typical FTTx Concept

FTTx Main features of the structure

As you can see from the diagram ,FTTH All are connected to the terminal by optical network , The terminal connected with this is called optical network terminal (ONT).FTTB or FTTC Connect to the building through optical network (Building) Or roadside (Curb), Then connect to the terminal through copper twisted pair network or wireless , The end equipment of optical network is called optical network unit (ONU), from ONU Connect to the network terminal through copper twisted pair network or wireless (NT).FTTCab And FTTC be similar , It's just that ONU It is located in the telecommunication transfer box (Cabinet) in . In the picture FTTB、FTTC、FTTCab All belong to “ part ” Fiber to home , That is to say, the optical fiber is not directly connected to the end user , Instead, it arrives near the end user , Then connect to the end user through the twisted pair network . stay FTTCab in , In the telecommunication handover box ONU Usually far from the end user 1000～2000m, In this case a ONU The unit can support about 500 End users . stay FTTC in ,ONU Closer to the end user , by 200—1000m, Can support 8～32 End users .OLT and ONT／ONU The network between them is called optical distribution network ODN, The distance can reach 20km, As shown in the figure .

FTTH Related terms

FTTH（Fiber to the Home） Fiber to home

FTTB（Fiber to the Building） Optical fiber to the building

FTTO（Fiber to the Office） Optical fiber to the office

FTTC（Fiber to the Curb） Fiber to the side of the road

ODN（Optical Distribution Network） Optical distribution network

OLT（Optical Line Terminal） Optical line terminal

ONU（Optical Network Unit） Optical network unit

PON（Passive Optical Network） Passive optical network

EPON（Ethernet Passive Optical Network） Passive optical network based on Ethernet

GPON(Gigabit-capable Passive Optical Network Gigabit capacity passive optical network

NT(Network Terminator) Network terminal

ONT(Optical Network Terminator) Optical network terminal , Electronic equipment located in the user's house

P2MP（Point to Multipoint） Point to point

CO（Center Office） Central office , The central location where services are provided

FTTH Market situation

stay 12 month 3 Japanese 2020 FTTH In a virtual conference ,IDATE And FTTH Council Europe Made up of 2020~2026 FTTH Market forecast data representation , To 2026 year , 27+ The number of subscribers in EU and UK countries will further increase to about 1.48 Billion , and 38+ The number of subscribers in EU and UK countries will reach about 2.08 Billion ,FTTH/B The coverage of will be in 2026 reach 73.3％, And 2012 Year of 23.4％ It is obviously higher than that .

It is predicted that the number of users in some countries is similar to 2019 The year-on-year comparison will show a sharp increase , Germany, for example, will grow +730%, UK growth +548%, Italian growth +218%. Judging from the country ranking , Russia may continue to lead , But Germany is expected to rank in 2026 It rose to the second , stay 2020 In the ranking of , Germany ranks eighth .

FTTH market prediction

FTTH European market ranking

FTTH Technology development

FTTH As an access technology , Now it has been recognized , The technology has matured .FTTH There are two common fiber access technologies ,P2P（ Peer-to-peer technology ） as well as P2MP（ Point to many PON）.

P2P（Peer-to-peer） It is point-to-point network technology , Can make no public network IP Direct communication between two users of .

PON(Passive Optical Network) It is passive optical network , Referring to OLT（ Optical line terminal ） and ONU（ Optical network unit ） Between ODN（ Optical distribution networks ） No active equipment , Use only fiber and passive components .PON It mainly adopts point to multipoint network structure , It's the realization of FTTB/FTTH The main technology of .

PON Technology can be divided into narrowband applications TDM Narrowband for service access PON Technology and broadband access based on ATM The transfer of BPON（APON）、 be based on Ethernet Packet transmitted EPON Technology and consideration ATM/Ethernet/TDM Comprehensive GPON technology . These three have been commercially realized FTTX Of PON technology .

FTTH Technology development

Optical access network ODN brief introduction

What is? ODN？ODN It is an optical distribution network , yes OLT and ONU Physical channels for optical transmission between , The main function is to complete the bidirectional transmission of optical signal , It's usually made of fiber optic cables 、 Optical connectors 、 It consists of optical splitter and supporting equipment for installing and connecting these devices , One of the most important parts is the splitter . Optical distribution network (ODN) There are two main ways to split light ： Primary and secondary spectroscopic .

Primary and secondary spectroscopic

The structure of the primary beam splitter is OLT- Spectroscope -ONU, from OLT To ONU The beam splitters between them are all in parallel . When first-order spectroscopic method is adopted , The splitter is generally set at the optical junction of the wiring . The structure of the secondary beam splitter is OLT- Spectroscope 1- Spectroscope 2-ONU, from OLT To ONU There is a cascade between the beam splitters . When two-stage light splitting is adopted , The first stage splitter is generally set at the optical junction of the wiring , The second stage splitter is generally set at the fiber distribution box .

Only one beam splitter can be connected to the primary beam splitter , Generally, the splitter with a large number of light splitters is selected , Such as 1:32 or 1:64. The secondary beam splitter is generally selected at the primary beam splitter 1:8 or 1:16 Splitter , The secondary beam splitting point adopts 1:4 or 1:8 Splitter . Usually , The primary spectroscopic solution is used in crowded downtown or urban areas , To reduce costs and make it easy to maintain optical fiber distributed networks （ODN） node . On the other hand , Secondary spectroscopic solutions for roadside or rural locations , To cover a wide range of ODN node , Save resources and money .

Primary and secondary spectroscopic

Working principle of optical splitter

The optical splitter is FTTH A core passive component in the system . Optical splitter is also called optical beam splitter , It is an integrated waveguide optical power distribution device , One input optical signal can be shunted into two or more output optical signals , The optical input power is evenly distributed on all output ports . for example , A spectral ratio is 1:4 The optical splitter can divide an optical signal into four parts on average , Then it is transmitted in four different channels . at present , The light splitting ratio of the optical splitter is generally 1：N or 2：N , Such as 1:4、1:8、1:16、1:32、2:16、2:32.

The working principle of the optical splitter is ： When a single-mode fiber conducts optical signals , The energy of light is not entirely concentrated in the fiber core , A small amount is transmitted through the cladding near the core , in other words , If the cores of two optical fibers are close enough , The mode field of light transmitted in one fiber can enter another fiber , The optical signal is redistributed between the two optical fibers .

Working principle of optical splitter

Optical splitter VS WDM Wavelength division multiplexer

To put it simply ,WDM The wavelength division multiplexer is a series of devices that carry information 、 But optical signals of different wavelengths are combined into a beam , Along a single fiber ; At the receiving end, use some method , Communication technology that separates optical signals of different wavelengths . This technology can transmit multiple signals on one optical fiber at the same time , Each signal is transmitted by a certain wavelength of light , This is a wavelength channel . In the same optical fiber, two or more optical wavelength signals simultaneously transmit information through different optical channels , The technology called optical wavelength division multiplexing is WDM. The splitter is used to divide the light of one wavelength into multiple beams for propagation .

Classification of optical splitter

According to the principle of light splitting and the difference of manufacturing process , Optical splitter can be divided into fused taper type （FBT） Planar waveguide type （PLC） Two kinds of .

PLC Optical splitter

Planar waveguide optical splitter （PLC Splitter） It is an integrated waveguide optical power distribution device based on quartz substrate , Its main function is to divide the optical signal from one optical fiber to multiple optical fibers . The device is composed of an optical splitter chip and an optical fiber array at both ends , Chip is the core component , The quality of the chip and the shunting channel directly affect the price of the whole shunter , The chip has an input and N Output waveguides . The fiber array is located on the upper surface of the chip , Seal the housing , A component has an input and N An optical splitter for outputting optical fibers .

PLC Optical splitter

Fused taper type （FBT） Optical splitter

Fused taper drawing technology is to bundle two or more coated optical fibers together , Then melt and stretch on the taper machine , And monitor the change of the split ratio in real time , After the spectroscopic ratio reaches the requirement, the melt drawing is finished , There's a fiber left at one end （ Cut off the rest ） As input , The other end is used as multi-channel output .

Fused taper type （FBT） Optical splitter

FBT VS PLC

The distribution of the spectral ratio is also one of the main differences between the two . The spectral variability of the tapered splitter is the greatest advantage of this device .PLC The splitters are equally divided , Signals can be evenly distributed to users . for example ,1×32 Of PLC The splitter can divide the optical signal into 32 Share , And then in 32 Transmission in different channels . Sometimes , Due to the inconsistency of the number and distance of users , It is necessary to allocate the optical power of different lines , At this point, devices with different spectral ratios are needed , Will use FBT Splitter .

FBT VS PLC

PLC Classification of optical splitter

Besides , The optical splitter can also terminate different types of connectors , The packaging method is usually box type or stainless steel tube type , The box type optical splitter is generally used 2mm or 3mm Optical cable with outer diameter , Stainless steel tubular optical splitter is generally used 0.9mm Optical cable with outer diameter .

Device structure

Bare fiber type PLC The optical distributor leaves bare optical fibers at all its ends . It is mainly applicable to the occasion of infrequent disassembly , Such as cable connector box 、 Optical fiber distribution board, etc .

Bare fiber type PLC Optical splitter

Micro package structure

The miniature optical splitter is a miniature steel tube package , It can be divided into tail fiber with connection head and tail fiber without connection head . Connectors usually have SC、LC、FC and ST type . It can be installed in the optical cable connector box , Module box , Distribution box .

Miniature optical splitter

fan-out PLC Splitter

fan-out PLC Shunts are commonly used 0.9mm Optical fiber , Through a bunch of fan out kits , Branch out a single fiber , Different types of connectors can be terminated . It can be effectively installed on the optical fiber DP box 、 In optical fiber connector box or other small terminal box .

fan-out PLC Splitter

ABS Box type PLC Splitter

The box type splitter is the type most used by various operators at present ,ABS Compact packaging , More flexible application .

ABS Box type PLC Splitter

Rack PLC Splitter

Rack mounted optical splitter is standard 19" Cabinet installation design , It can meet the requirements of data center or server room for high wire density . Generally, it is enclosed in a metal box , It is easy to install in optical fiber engineering , Yes PLC The splitter device plays a good protective role . There are various adapter mounting interfaces such as SC, LC, FC or ST The connector . Rack mounted optical splitter is widely used in FTTX project , Cable TV system and data communication center .

Rack PLC Splitter

Wall mounted PLC Splitter

Wall mounted PLC The box body of the distributor usually adopts ABS material , Direct connection of optical fiber 、 Termination or branch connection provides reliable protection . Double layer structure , The upper level is PLC Splitter , The lower layer is a melt fiber disk . The wall mounted optical splitter is used in FTTH In the terminal access link of the access system , For connecting and protecting optical devices . Wall mounted optical splitter is suitable for corridor 、 Basement and machine room, etc , It is also suitable for outdoor wall hanging and pole mounting .

LGX type PLC Splitter

LGX The optical splitter is encapsulated in a small metal box , Can be installed to 19 Inch 1U/2U/3U Inside the rack , Input / output pigtail structure , Can be easily connected to ODF Panel adapter , Save time .LGX Compact micro design , Plug and play , It can be conveniently installed in the optical fiber distribution box ,ODF subframes , Optical fiber terminal box and optical cable junction box .

LGX type PLC Splitter

Insert PLC Splitter

Insert PLC The splitter is installed and fixed in the cassette , The interface types are SC/FC/LC etc. . Mainly applicable to FTTH Corridor or outdoor light distribution point under access mode . frequently-used 1X4, 8, 16, 32 and 2X8, 16, 32 PLC splitters As a plug-in disk, it is used to install in the customer specific chassis , Especially the corridor box .

Insert PLC Splitter