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EPON Based On Ethernet Access Technology

EPON Based On Ethernet Access Technology

EPON is based on long-distance optical fiber transmission network Ethernet access technology. EPON uses multipoint architecture, an optical fiber carrying data signals down the line, after 1: N optical splitter signal into N Road, branch coverage of light multiple access point or access users.

EPON network structure

EPON and GEPON term in tradition, there is not a state error. Early EPON equipment industry is based FE bus, bus-based EPON equipment GE launched, in order to distinguish called GEPON, EPON equipment industry at present is essentially based on GE bus. At present basically referred to EPON.

A typical system consists of EPON system is composed of OLT, ONU and ODN. EPON network structure. OLT in the center machine room, it can be seen as a L2 switch or L3 routing switch. In the downstream direction, OLT to provide for passive optical network (ODN) optical interface; In the upstream direction, OLT will provide GE optical or electrical interface, the future of 10Gbit/s Ethernet technology standards after setting, OLT will also support a similar high-speed interface. In order to provide multi-service access, OLT also supports E1 and OC3 interfaces, to achieve the traditional voice access or circuit relay service.

In terms of EPON network management, OLT is the main control center, the built-in OAMP Agent, can manage the ONU in its terminal equipment, to achieve the five functions of network management. EPON network management can be defined on the OLT through the user bandwidth parameter to control the quality of user services by writing an access control list to implement network security control, by reading the MIB to obtain system status and user status information, but also provide a valid user isolation.

ODN is the optical distribution network, composed of passive optical splitter and fiber composition. The passive optical splitter is connected to the OLT and the ONU passive device, its function is to distribute the downlink data and uplink data centralized. The deployment of passive optical splitter is quite flexible, because it is a pssive device, be adapted to almost all environments. Generally passive optical splitter ratio has 1:2,1:4,1:8,1:16,1:32,1:64 so on. General recommended a splitting, splitting up not more than two.

ONU is placed on the customer premises side of the terminal device, EPON ONU in the Ethernet protocol, the realization of the second layer of low-cost Ethernet switching. The use of the Ethernet protocol, the process of the communication protocol conversion is no longer necessary to achieve the ONU transparent transmission of user data. Between the OLT to the ONU using encryption protocol to ensure the security of user data.

Based on EPON FTTH’s advantage lie in its strong converage, as far as covering up to 20 km (1:32 split ratio), starting from the end office, after OND connecting the optical access point.
Traditional optical access network, optical fiber extends the range to the network access point cutoff general, to achieve fiber to the home, you need to configure a large number of the access point port access layer switch expensive. With the passive optical network technologies emerge and mature, especially now that the EPON technology that can provide fiber tip directly to the user’s economically viable solution, FTTH become efficient access. In FTTx solution based on EPON, the introduction of how to solve the optical cable to the building, community, planning OLT, ODN, indoor user terminal (OUN) optical fiber connection becomes key.

EPON uplink and downlink technology

Between the OLT and ONU EPON using a single optical fiber to provide symmetric 1.25Gbps bandwidth limitations by physical interface, the actual provision of 1Gbps bandwidth to transmit data, voice and video services. EPON in a singel fiber using WDM technology, the upper and lower rows of data streams are transmitted in different frequency bands. Among them, the downstream 1490nm, upstream 1310nm, 1550nm optional for CATV.

Downlink data stream using broadcast, OLT will be 802.3 Ethernet frame format data flow through unicast replication pushed all the way at the ONU; ONU Ethernet frame header by determining where the OLT assigned LLID (Logical Link ID ) to determine whether the received data frame received their own, their data will not discard the frame.

Upstream data stream using time division multiple access (TDMA) technology, the uplink time into a number of time slices, according to the allocated bandwidth and service ONU priority to the ONU upstream data streams are allocated different time slots, each time point the optical fiber transmission is only one ONU upstream data streams. Negotiated between the OLT and ONU, ONU upstream avoid conflicts between, will not cause data loss. Shown in Figure 3.

EPON and ADSL comparison

ADSL After several years of vigorous development, has become China’s most popular fixed-line operators in broadband access means. ADSL using traditional copper broadband data transmission resources, make full use of the fixed-line operator’s copper resources, China Telecom and China Netcom such operators, the early development of broadband access is one of the best choices.

ADSL/ADSL2 + Business is an asymmetrical transmission of broadband access technologies, the uplink bandwidth is limited, less than 1M, downstream bandwidth up to 26Mbps, the actual business of covering no more than 3km distance, generally offer 512Kbps to 2Mbps downstream bandwidth, the main application the public Internet.

However, with a variety of new businesses, especially the rise of video services, the user’s bandwidth requirements are increasing. With the long, online games, instant messaging, broadband telephony, video telephony, personal photo album sharing applications such as the rapid growth of users of the upstream bandwidth demand is also growing.

China Telecom and China Netcom broadband network in the planning of their future bi-directional bandwidth of individual users will reach 10M-20M. ADSL bandwidth strictly limited by the transmissioin distance, the higher the bandwidth achieved only over short distances, even after the “Light of Copper” reform, reducing the coverage of ADSL, which is only in a certain period of time, to a certain extent bandwidth requirements.

Based on fiber access networks, the bandwidth is theoretically unlimited extension. So with the EPON technology matures, its high bandwidth, long distance coverage, making EPON technology replacing ADSL technology will become the inevitable choice.

Relative ADSL, EPON at relatively high initial construction expenditures, including pre-laying equipment costs and fiber costs. However, due to network using passive optical network technology, fiber-based PON technology in the operation and maintenance of the costs to be much lower than ADSL and copper wire.

By the late operation and maintenance cost is reduced, provide higher bandwidth and more long-distance business coverage, and the resulting ability to provide more new business, bring more revenue, can be relatively offset on the cost of equipment and wiring. The fiber cost is already very low, FTTx has entered a golden period of development, the cost of equipment will also continue to reduce in the building. Thus, through the deployment of EPON carriers can be enhanced, including broadband access, including a comprehensive business competitiveness, thereby stabilizing the user resources, and even brought the loss of the user’s back, it will be for operators to bring more revenue, enabling operators to long-term benefit.

EPON technical advantages

With EPON technology matures, the industry mainstream operators have started large-scale deployment of EPON system, expand FTTx applications, and on this basis to achieve Triple Play (triple play, to deliver voice, data and video services), build triple play access platform.

Since 2004, the most developed in FTTH in Japan, Korea, Taiwan and the United States, Europe and other countries and regions, EPON technology has been large-scale applications, and further stimulate the IPTV business prosperity. In the Chinese market, the current EPON products have been held in all provinces of the pilot and commerical.

EPON technology uses wavelength division multiplexing (WDM) technology in a single fiber to achieve symmetrical 1Gbps bandwidth and client segments and can be implemented in close spectroscopic down, save a lot of backbone fiber resources. Currently the maximum achievable split ratio is 1:64. EPON system is another advantage lie in its strong coverage in the 1:32 split ratio furthest covering up 20km, at 1:64 next, as far as coverage bandwidth of each ONU user up to 30M or more, so that the video business has been enough bandwidth guarantees.

The use of passive optical splitter, save a lot of maintenance resources, saving room, power matching and other resources, reducing the overall cost of FTTx network construction and maintenance costs. In recent years, the cost of fiber optic drop cable for the FTTx provide supporting cost reduction.

At present the operators to provide broadband access services are mainly two kinds of ADSL and LAN access, in addition, with the increasing demand for bandwidth, VDSL is becoming an option. Other access methods, such as Cable Modem, power line access, etc. As the market share of small and are subject to industry resource constraints.

Industrialization of PLC splitter chip technology

Industrialization of PLC splitter chip technology

Fiber optic communication network has become the cornerstone of today’s world of information transfer. With the further development of the network and market demand for communication bandwidth increases, the entire communication network to the part between the user’s last ten km and last km, the network part is also being optical fiber. FTTH becomes an important direction of the development of fiber optic communication network.

FTTH mainly uses PON network technology, which requires a large number of low-cost optical splitters and other optical passive. Optical splitter device is an integral part of FTTH, and with the promotion of FTTH, there would be a great market demand. The traditional preparation of optical splitter technology is fiber fused biconical taper (FBT) technology. Its characteristics are mature and simple technology. The disadvantage is that the assigned ones too large, and the device size is too large, which causedthe decrease in yield and the rising cost of single channel, shunt reactive stars uniformity will deteriorate. FBT technology based fiber optic splitter preparation techniques have been unable to adapt to the market demand.

As you can see from the perspective of development of optical devices, PLC technology has become a mainstream technology for large-scale preparation of high-performance and low-cost optical splitter. It is the use of PLC technology, to produce the optical splitter chip, coupled with the optical fiber array package, complete the preparation of the optical splitter. Its features are: small size of the device, the cost is relatively low, splitter good uniformity, at the same time, the technical threshold is relatively high, especially for production of more than large ones optical splitter, suitable for mass production. It can ensure that the light emitting device miniaturization, low cost and high performance. Analysis of PLC technology, you can see that the glass-based PLC technology has great advantages in terms of equipment investment, production costs, the optimal choice of production required for fiber-to-the-home, low-cost optical devices such as optical splitter.

International, PLC technology has been widely used in the miniaturization, high-performance optical device fabrication and production, in particular, the optical splitter chip. In China, however, the reality is that we have become a PLC encapsulation big country, but is limited to the optical splitter and optical device fabrication device coupled packaging and downstream industry chain, no one PLC chip Health line, PLC core device chip entirely dependent on imports. Which there is a problem that the core preparation technique of the PLC device lies in the outward, this has resulted in major cost control of the device is limited in the chip at the same time, which also led to the lack of technical support further to the high-end integrated chip development, severe hinder the development of our country in the PLC application.

PLC splitter chip manufacturing process PECVD (plasma enhanced chemical vapor deposition) and FHD (flame hydrolysis deposition) and ion exchange. The former two with the substrate material is a silicon-based silica, and the latter with the substrate material is glass. AWG (arrayed waveguide grating) chip production, Silica optical waveguide splitter chips can be produced on silica on silicon waveguide or glass waveguide. Production by ion exchange glass waveguide PLC chip domestic number of colleges and universities have been conducting research and development, technical appraisal sample has been reached the international advanced level of similar products. The breakthrough of the results from the glass material, preparation equipment, process conditions designed to chip a full range of core technology to master the the buried low loss and low polarization characteristics PLC chip core preparation techniques.

Characteristics of the technology investment, equipment operation and low maintenance costs, simple process conditions, the production of optical passive low transmission loss and polarization characteristics with matching coupling of the fiber loss, environmental stability, and manufacturing costs low, very suitable in need of the PLC production line, can be used for producing low-cost fiber-to-the-home integrated optical splitter chip. Further pilot research and development, to solve adapted to the production of core technology, will be able to achieve your PLC splitter chip mass production.

In fact, in addition to the production of optical splitter chip, glass-based PLC technology R & D production environment with a wide range of other potential applications, for example, can be applied to detect the required light sensor.

Source: FiberStore

Fiber Optic Transmission

Fiber Optic Transmission

Optical fiber may be the medium of choice for high capacity digital transmission systems and speed local area network. Besides these applications, optical fiber is also used to transmit microwave signals for cable tv, cellular radio, WLAN and microwave antenna remoting. To deliver microwave over optical fiber, the microwave signal is converted into optical form in the input from the fiber and at the creation of the fiber, it’s converted back to electrical signal. The benefit of fiber transmission of microwave is reduced losses in accordance with metallic media (e.g. copper coaxial cable). This leads to longer transmission distance without signal amplification or utilization of repeaters.

There are two approaches to optical signal modulation and recovery. The very first type is IMDD (Intensity Modulation Direct Detection) and also the second type is Coherent Detection. In IMDD, the optical source intensity is modulated through the microwave signal and also the resulting intensity modulated signal passes through the optical fiber to a photodiode where the modulation microwave signal is converted to electrical domain. In Coherent Detection, the optical source is modulated in intensity, frequency or phase by the microwave signal. The modulated signal goes through the optical fiber towards the receiver where it is mixed with the creation of a local oscillator (LO) laser. The combined signal is converted to electrical domain using a photodiode. This produces an electric signal dedicated to the main difference frequency between the optical source and the LO laser (i.e. intermediate frequency). This signal is further processed to recuperate the analog microwave signal.

RFoG (Radio Frequency over Glass) is the cable operators’ implementation of microwave transmission over optical fiber where the coax portion of the HFC (Hybrid Fiber Coax) is substituted with a single fiber, passive optical network architecture (PON). RFoG allows cable operators to deploy fiber connectivity to customer premises (FTTP) while keeping its existing HFC and DOCSIS infrastructure. Such as the HFC architecture, video controllers and knowledge networking services are fed through a CMTS/edge router.

These electrical signals are then converted to optical and transported via a 1550 nm wavelength via a wavelength division multiplexer (WDM) and a passive optical splitter to a R-ONU (RFoG Optical Network Unit) located at the customer premises. R-ONUs terminate the fiber connection and convert the traffic to RF for delivery over the in-home network. Video traffic could be fed over coax to a set-top box, while voice and knowledge traffic could be delivered to an embedded multimedia terminal adapter (eMTA), The return path for voice, data, and video visitors are on the 1310 nm or 1590 nm wavelength to some return path receiver, which converts the optical signal to RF and feeds it back into the CMTS and video controller.

The benefit of radio-over-fiber technologies are that it centralizes the majority of the transceiver functionality by transmitting the microwave signals within their modulated format over fiber. This reduces the number of access suggests antennas with amplifiers and frequency converters. In-building passive picocell for GSM or UMTS is implemented using radio-over-fiber. Wireless base stations are located in a central communications room as well as their outputs/inputs fed through RF multiplexers to lasers/photodiodes contained within the optical transceiver hub. The modulated optical signals are linked to/from the remote antenna units (AUs) within the building using single-mode optical fiber. The bottom station utilizes a combined detector/optical modulator, that is directly coupled to the antenna, to ensure that no electrical amplification or any other processing is needed.


PLC Splitter Production and Packaging

PLC Splitter Production and Packaging

With the recovery of optical fiber communication industry and the development of FTTX, the spring of fiber optic splitter market is coming.

There are two types of optical splitter, which are Fused fiber splitter and PLC splitter. PLC splitter is a hot research today, with a good prospect of application. PLC splitter package, however, is the difficulty in manufacturing.

The PLC splitter Package refers to the planar waveguide splitter on the light guide path (waveguide) with the fiber in the fiber array aligned one by one, and then stick with specific adhesive (such as epoxy glue) together with the technology. Wherein the alignment accuracy of the PLC splitter and an optical fiber array is the key technology. PLC splitter package involves a six-dimensional optical fiber array and optical waveguides in close alignment difficult. When the manual, the drawback is the low efficiency, poor reproducibility, human factors and is difficult to achieve large-scale production.

PLC splitter Production
PLC splitter using semiconductor technology (lithography, etching, developing technology) production. Multi-channel optical fiber array and the optical waveguide array is located on the upper surface of the chip, branching function is integrated on-chip is a chip on the splitter 1,1; Then, the ends of the chip, respectively coupling the input terminal and an output terminal package.

Compared with Fused Splitter, PLC splitter has these advantages: (1) loss wavelength is not sensitive to light, to meet the different wavelengths of the transmission needs. (2) spectroscopic uniform signal can be uniformly allocated to the user. (3) compact structure, small size, can be installed directly in the various existing junction box, without leaving a lot of space for installation. (4) only a single device shunt channel can achieve much more than 32 channels. (5) The multi-channel, low cost, stars ones more and more obvious cost advantages.

At the same time, the main drawback of the PLC splitter: (1) device fabrication process complexity, high technical threshold, the chip by several foreign companies to monopolize the domestic bulk package produced by very few companies. (2) relative to the higher cost of Fused Splitter more at a disadvantage, especially in the low channel splitter.

PLC splitter Packaging Technology
PLC splitter package process includes coupling alignment and bonding operations. Coupling of the PLC splitter chip and the optical fiber array is aligned with both manual and automated, and they depend on the hardware with the six-dimensional precision trimming frame, the light source, power meter, microscopic observation system, while the most commonly used are self-aligned , it is through the optical power feedback closed-loop control is formed, and therefore high coupling efficiency docking accuracy and docking.

PLC splitter has 8 channels and each channel must be accurately aligned to ensure that the relative position between the respective channels due to the manufacturing process of the waveguide chip and an optical fiber array (FA), so only the PLC splitter and the first channel of the FA and 8-channel simultaneous alignment can ensure that other channel aligned, thus reducing the complexity of the package. The most important in the packaging operation at the technical difficulty is the highest coupling alignment operation, it comprises two steps First Harmonic precise alignment. First tune the purpose is to enable the waveguide to light through; the purpose of precise alignment is precise positioning of the completion of the preferred optical power of the coupling point, and it is realized by the program to search the maximum optical power.

Contrast FBT with PLC technology used in Optical Splitters

Contrast FBT with PLC technology used in Optical Splitters

Optical splitter is suitable for a fiber optic signal to be decomposed into multi-channel optical signal output.

Role of optical splitter
(1) It divides out a main light source into 1-N optical path.
(2) It synthesizes 1-N optical path into a main light source and recovers this source.

Working principle
In the single-mode optical fiber of the optical signal when the energy of the light is not completely concentrated in the core communication, a small amount is spread through the cladding near the core, that is, in the two fibers the core sufficiently close, then the mode field of the light transmitted in an optical fiber can enter another one optical fiber, optical signals in the two optical fibers to obtain a re-allocation

There are two types of optical splitters to meet the need for spectroscopy. One is fused biconical taper splitter (FBT Splitter) made by the traditional optical passive device manufacturers using the traditional biconical taper coupler technology. The other one is planar optical waveguide splitter (PLC Splitter) based on optical integration technology. Both devices have their own advantages. Depending on the occasion and demand, users can rationally choose different types of spectroscopic devices following a brief introduction of the two devices, which is just for reference.

FBT Splitter
Fused biconical taper (FBT) technology is tied to two or more fibers, and then melted in a cone machine, pull tensile and real-time monitoring of changes in splitting ratio, melt tensile splitting ratio to meet the requirements end, wherein one end of a fiber optic reserved ( The remaining cut off) as the input terminal and the other end a multitude of road outputs. Mature tapering process can only pull 1 × 4. 1 × 4 or more devices, with a plurality of 1 × 2 connected together. Then the whole package in the splitter box.

Main advantages
(1) The taper coupler has more than 20 years of history and experience, many equipment and process just follow it, development funds only a few one-tenth or even a few hundredth of PLC
(2) Raw materials have easy access to the quartz substrate, optical fiber, heat shrink tubing, stainless steel pipe and less plastic, a total of not more than one U.S. dollars. investment in machinery and equipment depreciation costs less, 1 × 2,1 × 4 the low channel splitter low cost.
(3) Splitting ratio can be real-time monitoring, you can create unequal splitter.

Main drawback
(1) Loss of the optical wavelength-sensitive, generally according to the wavelength selection device, which in the triple play during use is a fatal defect, since the optical signal transmitted in the triple play there 1310nm, 1490nm, 1550nm multi kinds of wavelength signals.
(2) Poor uniformity, 1×4 nominal about 1.5dB away, 1 × 8 or more away from larger, can not ensure uniform spectroscopic, which may affect the overall transmission distance. A demultiplexer
(3) Insertion loss varies with temperature variation is greater (TDL)
(4) The volume is relatively large, so the reliability will be reduced, and the installation space is restricted.

PLC Splitter
The planar waveguide technology using a semiconductor production process, the optical waveguide branching device branching function is completed on the chip, and can be implemented on one chip up to 1X32 splitter, then, at both ends of the chip package input terminal and an output coupled respectively end multi-channel fiber optic array.

Main advantages
(1) Loss is insensitive to the wavelength of transmitted light, to meet the different wavelengths of the transmission needs.
(2) Splitting the uniform, the signal can be uniformly assigned to a user.
(3) Compact structure, small size (Borch 1 × 32 size: 4 × 7 × 50 mm), can be directly installed in the various existing junction box, no special design leave a lot of space for installation.
(4) Only a single device bypass passage can achieve much more than 32 channels.
(5) The multi-channel, low cost, stars ones more and more obvious cost advantages.

Main drawback
(1) Device fabrication process complexity, high technical threshold, the chip is several foreign companies to monopolize domestic bulk package production enterprise only Borch rarely several.
(2) Relative to the higher cost of Fused Splitter more at a disadvantage, especially in the low channel splitter.

Contrasting the main parameters of the two devices

(1) Both devices have their own advantages in terms of price and performance. The two technologies are constantly upgraded, continue to overcome their disadvantages. Pull cone splitter being addressed disposable tapering in small quantities and poor uniformity; the waveguide splitter also reduce the cost to make unremitting efforts, the two devices 1X8 cost almost the same, with channels increase in the price of a planar waveguide splitter better.

(2) How to choose the two devices? The key is the occasion and the needs of users in terms of. In volume and the wavelength of light is not very sensitive applications, especially in the case of shunt less, the choice of tapering optical splitter relatively affordable, such as independent data transmission is optional 1310nm pull cone splitter, TV video network Select the the 1550nm pull cone splitter; triple-play FTTH require multiple wavelength optical transmission and more occasions should be used in the optical waveguide splitter. At present, the majority of domestic companies FTTH trial network multi-pull cone splitter, which is due to the many designers are not familiar with the PLC device, the few domestic companies producing such devices. Japan and the United States FTTH really commercial operation of the market is almost entirely planar optical waveguide splitter.