Data Transmission over Polymer Optical Fibers

I. Tafur Monroy, H.P.A. vd Boom, A.M.J. Koonen, G.D. KhoeCOBRA Institute, Eindhoven University of Technology, P.O. Box 513, Eindhoven, The Netherlands, E-mail:

i.tafur@tue.nl.

Y. WatanabeAsahi Glass Company, Tokyo, Japan. E-mail: y_wata@agc.co.jp.

Y. Koike, T. IshigureKeio University, Faculty of Sciences and Technology, Japan. E-mail: koike@appi.keio.ac.jp.

Abstract

Polymer Optical Fiber (POF) is a promising transmission medium for providing broadband telecommunication services within the customer’s premises. POF offers several attractive features for data transmission such as broad bandwidth and low cost for in-house, access and LAN applications. This article presents a review on optical transmission systems using POF and their enabling technologies. A summary is given of experimental data links with record capacity over record transmission distances. Standardization activities in POF technology and transmission are reported. To conclude, we discuss trends for further development and research.

Keywords: Optical communications, in-house networks, POF, polymer optical fiber.

Dr.ir Idelfonso Tafur Monroy

Eindhoven University of TechnologyTelecommunications Technologyand ElectromagneticsP.O Box 513, EH 11:085600 MB EindhovenThe Netherlands

Tel: + 31-40-2473219Fax: +31 -40 -2455197

Data Transmission over Polymer Optical FibersI. Tafur Monroy, H.P.A. vd Boom, A.M.J. Koonen, G.D. Khoe

COBRA Institute, Eindhoven University of Technology, P.O. Box 513, Eindhoven, The Netherlands, E-mail: i.tafur@tue.nl.

Y. WatanabeAsahi Glass Company, Tokyo, Japan. E-mail: y_wata@agc.co.jp.

Y. Koike, T. IshigureKeio University, Faculty of Sciences and Technology, Japan. E-mail: koike@appi.keio.ac.jp.

Abstract

Polymer Optical Fiber (POF) is a promising transmission medium for providing broadband telecommunication services within the customer’s premises. POF offers several attractive features for data transmission such as broad bandwidth and low cost for in-house, access and LAN applications. This article presents a review on optical transmission systems using POF and their enabling technologies. A summary is given of experimental data links with record capacity over record transmission distances. Standardization activities in POF technology and transmission are reported. To conclude, we discuss trends for further development and research.Keywords: Optical communications, in-house networks, POF, polymer optical fiber.

1 Introduction

There is an increasing demand for high data-rate communication in the costumer’s premises and office areas to provide services like fast internet access and compressed digital video based services (MPEG). The transmission media used at present are not suited for provisioning high-bandwidth services at low cost. For instance, today’s wiring in local area networks is based mainly on copper cables (twisted-pair or coaxial) and glass fiber of two kinds: single mode and multimode. Copper based technologies suffer strong susceptibility to electromagnetic interferences and have a limited capacity for digital transmission. Conventional silica based fibers are a costly solution because they require precise connecting and dedicated installation and handling. An alternative technology is the use of polymer optical fiber (POF) for data transmission [1]. POF offers several advantages over conventional transmission media: large bandwidth over short distances (up to 1000 m), potential low cost associated with ease of installation, splicing and connecting. Furthermore, POF has small volume and light weight. It guarantees electromagnetic immunity. In addition, POF is not brittle but ductile and will stretch rather than break under increased tension; even a thick bundle of POF is more flexible than a bundle of glass fiber. POF technology could be used for data transmission in many application areas ranging from in-house networking to the avionic environment deploying a variety of techniques [2]. This article serves as a review on data transmission systems over POF and their enabling technology.

This paper is organized as follows. Firstly, the transmission properties of POF such as attenuation and bandwidth are discussed. A review on the advantages of POF over conventional transmission media is presented. Secondly, we present a list of record

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transmission experiments, including wavelength division multiplexing (WDM) transmission, that demonstrates the feasibility of POF technology for high capacity systems.

Figure 1: Spectral attenuation of PF POF.

Comprehensive experimental details are given to expose several issues that are relevant for the system performance. Thirdly, we report on standardization activities regarding POF technology and transmission. Finally, the potentials of POF technology for data transmission are discussed and summary conclusions are drawn.

2 Polymer optical fibers

Polymer optical fibers used for data communications are made mostly of polymethyl methacrlylate (PMMA) and perfluorinated (PF) polymer material. Conventional PMMA-POF has a step index (SI) profile. SI PMMA-POF has been commercially available for many years. The core diameter of this fiber is typically 0.125-2.0 mm. This fiber has a large attenuation (150 dB/km at 650 nm wavelength) and limited bandwidth e.g. 20 MHz.km. Improvement in the bandwidth of this POF fiber has been obtained by grading the refractive index. Graded index (GI) PMMA-POF has shown a bandwidth-distance product of 0.5 GHz.km at the 650 nm wavelength.

Although by grading the index profile of significantly enhanced characteristics have been obtained, the bandwidth and attenuation still limit the transmission distances and capacity. Reduction of transmission loss has been achieved by using amorphous perfluorinated polymers for the core material. This new type of POF has been named perfluorinated POF (PF-POF). This new fiber with low attenuation and large bandwidth has opened the way for high capacity transmission over POF based systems. A cable of two fibers of GI PF-POF has

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0.1

1

10

100

1000

10000

0.4 0.6 0.8 1.0 1.2 1.4 1.6Wavelength (m)

PMMA based GIPOF

PF polymer based GI POFExperimental spectrum

PF polymer based GI POFTheoretical spectrum

been commercially available since June 2000 under the trademark Lucina [3]. For a review of the evolution of POF performance see [4]. The typical characteristics of GI PMMA POF and GI PF-POF are summarized in Table 1.

2.1 Attenuation

Figure 1 presents of the dependence of the attenuation of POFs on the wavelengths. A significant point to note is that perfluorinated POF promises low attenuation (less than 40 dB/km) over a wide spectral window of wavelengths ranging from the 650 nm to 1310 nm. This allows for enhancement of transmission capacity by using WDM techniques and use of the same wavelengths as in glass optical fiber systems. State-of-the-art GI PF-POF shows an attenuation value in the order of 10 dB/km and a bandwidth-distance product of 1 GHz.km[1].

Characteristic GI PMMA-POF PF GI-POF

Attenuation 150 dB/km at 650 nm

>1000 dB/km at 850 and 1310 nm

<40 dB/km at 650-1310 nm. 10 dB/km achieved at 1210 nm

Potential bandwidth distance product

2 GHz.km at 650 nm. 10 GHz.km

Achieved transmission distance

200 m at 2.5 Gbit/s 550 m at 2.5 Gbit/s 110 m at 11 Gbit/s

Table 1. Summary of characteristics of GI PMMA and GI PF-POF.

2.2 Bandwidth of POF

Apart from attenuation, an important characteristic of POF as transmission medium is its bandwidth. Bandwidth is a measure of the transmission capacity of a fiber data link. Several factors determine the bandwidth of polymer optical fiber. These include chromatic dispersion, modal dispersion, and launching conditions. Launching conditions refer to how light is coupled into the fiber; for example its angular light power distribution. The bandwidth characteristic is usually specified by the –3 dB bandwidth. The –3 dB bandwidth is determined by analyzing the POF transfer function, which relates the output signal to the input one in an optical fiber considering it as a transmission line. Dispersion in POF may be divided into two main types: chromatic and modal dispersion. Chromatic dispersion is related to the dependence of the index of refraction on the wavelength and the dependence of the mode intensity profile on the wavelength. Therefore, the various spectral components of each mode propagating in the fiber travel at a different speed, depending on the wavelength. This results in pulse broadening; i.e. dispersion. Modal dispersion is related to the spreading of the pulse as a result of the difference in propagation delays among the modes as well as dispersion from intermodal effects such as power mixing between modes and mode dependent loss. In addition, modal dispersion is dependent on how the modes are excited (the launching condition), the spectral characteristics of the light source, and on the effects of micro-bending, among others. It is interesting to note that material dispersion of PF-POF fiber is smaller than

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that of silica fiber [5]. So an optimized GI PF-POF may outperform a graded index silica fiber at the optimum-operating wavelength.

An accurate analysis of dispersion in POF is required to establish its bandwidth limitations and to identify ways to get improved characteristics. In references [6,7] a comprehensive theory is presented for dispersion in graded-index optical fibers. The analysis in [6] includes most of the effects influencing the bandwidth of GI fibers; both chromatic and modal contributions. Modal delay, distributed loss and mode coupling are also taken into account. In [1] it is predicted that a PF GI-POF whose index profile is optimized to minimize dispersion is able to achieve a bandwidth-distance product in the order of 10 GHz.km.

3 Applications

Application areas that may benefit from the use of POF for data transmission include those covering short transmission distances; typically ranging from 100 to 1000 meters. POF can transport data traffic with bit rates varying from hundreds of Mbit/s to 10 Gbit/s. POF technology has good prospects for application in areas where the cost is a driving factor, as well as where easiness of handling and installation is mandatory, like in office and residential area networks. A short inventory where POF may be considered for installation includes:

a) In-home and access networks

b) Fiber to the apartment

c) Wireless LAN backbone

d) Office LAN and horizontal wiring

In areas where enhanced transmission capacity is required, parallel fibers may be used or WDM transmission can be introduced to increase capacity. POF is also of interest for areas where electromagnetic immunity is required such as in the case of the automotive and aerospace industry where its low weight is of importance. In section 7 we will discuss the potentials of POF technology for deployment at the customer's premises.

3.1 POF versus other technologies

There are several technologies that can serve as the transmission medium for broadband services at the customer's premises such as twisted copper pairs and copper coaxial cables, silica single mode fiber, and multimode glass fiber based technologies. Let us examine the advantages and disadvantages of POF with respect to each of those technologies.

Compared to copper based technologies like coax cables and twisted pair, POF guarantees electromagnetic immunity and absence of crosstalk. POF has smaller volume, it is less bulky, more flexile, and it has smaller weight. With respect to data transmission capability, POF offers higher bandwidth at longer transmission distances and it offers lower installation and maintenance costs particularly in splicing.Compared to multimode glass optical fiber, POF is more flexible and ductile making it easy to handle. POF termination can be realized faster and cheaper than in the case of multimode glass fiber. The typical large core of polymer fiber allows for large tolerance on axial misalignments, which results in cheaper connectors. For comparisons sake, let us examine the power loss due to lateral (axial) misalignment of connecting two graded index (parabolic

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case) multimode fiber with different core diameters. Calculations, assuming uniform modal power distributions, for a misalignment of 25 microns yield a loss of 1.76 dB for a 62.5 microns core diameter multimode fiber (MMF). For the case of GI PF-POF with a core diameter of 200 microns the 25 microns displacement results only in 0.48 dB loss. These calculations are based on the theory of power coupling of two graded-index fibers[19].

Another advantage of large core PF GI-POF has been observed with respect to the bandwidth degradation due to modal noise at misalignments in fiber-to-fiber connections. Namely, GI PF-POF shows very short time delay at the wide area of the core. This is in contrast to the case of multimode silica fiber with 50 to 62.5 microns core where small displacements cause severe bandwidth degradation [1,20].

Attenuation and bandwidth characteristics of the current state-of-the art POF are not at par with those of standard single mode glass fiber; however they are superior to those of copper based technologies. Furthermore, the installation and termination of POF are easier and promise low costs compared to the single mode and multimode glass counterparts. It is worth noting that connectors for POF are not only easier to assemble compared to those for single mode and multimode glass fibers but are also easier than those for HF coax cabling. Termination of coax cabling requires a more skilled handling as improper termination will cause large loss, considerable increased ingress noise and high reflection levels. Moreover, POF connectors can be assembled easily for instance using a low cost plastic ferrule [8]. Coupling loss using the above method has been measured to be in the order of 0.8 dB at the 850 nm wavelength for a POF with a core diameter of 120 microns. 4 POF data link and system devices

In this section, we would like to review the components being used in experimental POF data links, such as light sources, detectors and couplers, etc. Most of the existing multimode glass fiber links use broadband light sources such as light emitting diodes (LEDs) and Fabry-Perot lasers. These sources have also been used in many reported experimental transmission links over polymer fibers. Recently, vertical-cavity surface emitting lasers (VCSELs) have been used for multimode fiber links and for experimental POF data trials. VCSELs are promissing to become a low-cost solution for light source for LAN applications [9-10]. An important element in a POF link is the coupling to the source and coupling to the detector. In laboratory trials, lenses are commonly used for this task. However, for deployment of practical links effective coupling devices should become available. The coupling from the large core POF to the detector is an important issue. Therefore, photodetectors with a large detection area and with high speed are preferred for POF data links. This is a challenging issue as detectors with a large sensitive area are usually slower than those with a small detecting area. Reported experimental trials commonly use large area avalanche photodetectors (APD).

Wavelength division multiplexing can be used to enhance transmission capacity. In this case, wavelength multiplexers and demultiplexers should be available. In laboratory trials, a set of dielectric thin-film filters has been used to perform the demultiplexing operation of optical channels in a POF data link [11]. The multiplexing of channels has been achieved by butt joining a bundle of small core fibers (pig-tailed to the light sources) to a single but large core POF fiber. For the case of multimode glass fiber link, a compact WDM transceiver has been proposed, based on the use of VCSELs, polymer waveguide demultiplexers and

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multiplexers[10]. Similar transceiver modules may become available for WDM POF data links.

Table 2: List of experimental transmission records using POF. PMMA: polymethy methacrylate; PF: perfluorinated polymer; TU/e: Eindhoven University of Technology; BL: Bell Labs, Lucent Technologies;Keio: Keio University, Japan; Ulm:University of Ulm, Germany.

Date Bitrate [Gbit/s]

Distance [m] Wavelength [nm] Fiber material

Mar. 1995 (Keio) 2.5 100 650 PMMA

Feb. 1998 (TU/e) 2.5 200 645 PMMA

Aug. 1998 (TU/e) 5 200 1310 PF

Oct. 1998 (TU/e) 2.5 300 645 PF

Nov. 1998 (TU/e) 2.5 550 1310 PF

Jan. 1999 (TU/e) 2.5 550 84 PF

Aug. 1999 (Ulm) 7 80 950 PF

Sep. 1999 (TU/e) 3 x 2.5 200 645,840,1300 PF

Mar. 2000 (TU/e) 2 x 2.5 328 840,1300 PF

Mar. 2000 (BL) 11 100 1310 PF

Jul. 2000 (TU/e) 2x2.5 456 840,1300 PF

May 2001 (TU/e) 1.25 990 840 PF

5 Data transmission experiments

In this section, we present a review of experimental POF data transmission links. Firstly, we present a list of world record transmission experiments using POF. Secondly, we present a detailed experimental set-up of a single channel POF transmission link and of a WDM transmission set-up. This detailed description is intended to expose relevant technological and system issues involved in high capacity data links over POF.

5.1 Record transmission experiments

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The experimental trials reported in Table 2 have demonstrated the feasibility of POF links for high capacity transmission. These trials represent record achievements in data transmission over POF and are in chronological order. The summary in Table 2 is by far not complete, however it highlights milestone results and clearly shows the improvements in achieved transmission capacity and link distances. From the results in Table 2 one can clearly see how POF technology has evolved in the past few years to its current state supporting high capacity data-rate transmission.

Figure 2: Experimental set-up for a transmission link over 550 m of GI PF POF.

5.2 Experimental details

Several laboratory trials have been performed to investigate the feasibility and the limits of data transmission over POF [11]. Several types of fiber have been used in systems operating at different data rates and reaching different transmission distances. To give insight into the technological aspects involved in POF data transmission experimental details and results are presented for the following configurations:

a) A GI PF-POF single channel transmission system. The data rate is 2.5 Gbit/s and it operates at 840 nm and 1310 nm wavelengths.

b) A system using WDM transmission techniques, operating at 645 nm, 840 nm and 1300 nm wavelength.

2.5 and 5 Gbit/s transmission experiments with PF GIPOF

Figure 2 shows the block diagram of the experimental set-up used for data transmission over 550 meters of GI PF- POF. Two wavelengths, single channel operation, were used for transmission at a bit rate of 2.5 Gbit/s. Light was launched into the fiber in such a way that only a few number of modes propagated in the fiber. This limited launching effectively increases the POF's bandwidth. The PF fiber showed an attenuation of 43.6 dB/km at 840 nm and 31 dB/km at 1310 nm. Asahi Glass Co. provided the sample of the PF polymer fiber used in this trial.

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In the experiment operating at 1310 nm a commercially available telecommunication laser, a distributed feed-back (DFB) laser, was used as the light source. At the receiver end, a very sensitive large active area (diameter of 230 microns) silicon APD was used together with a low loss interconnection between the GI-POF and the APD receiver. At the transmitter side, light from the single mode fiber (SMF) pigtail of the DFB laser was launched into the large core of the GI-POF by means of a butt coupling. The coupling loss was less than 0.1 dB. In the experiment involving the 840 nm wavelength, a VCSEL light source was used in combination with a silicon APD receiver. The VCSEL used had a modulation bandwidth of 2 GHz; for this reason an electrical equalizing circuit was used to enhance the bandwidth.

Fig. 3. BER measurements for a 2.5 Gbit/s data link over 550 m of PF GI-POF. Solid lines represent the curves for operation the 1310 nm wavelength, and the dashed lines for the system at 840 nm wavelength, respectively. B-B stands for back-to-back and Trans. for transmission over 550 m of POF.

Light was launched directly from VCSEL into the GI-POF with a resulting loss of about 1 dB. Both experiments (at the 840 and 1310 nm wavelength) were carried out using a non-return-to-zero (NRZ) pseudo random binary sequence (PRBS) with a pattern length of 223-1. Special measures were taken to avoid reflections back to the light source. A lens-based coupling system was used to improve optical coupling efficiency from the fiber to the photodetector. The bit-error rate (BER) as a function of the received average power at the input of the receiver was measured after transmission over 550 m of fiber and without fiber (back-to-

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back); see Fig. 3. In the 840 nm experiment (dashed lines in Fig. 3), the average output power of the VCSEL was 1.3 dBm and the sensitivity of the receiver was -28.6 dBm at 2.5 Gbit/s for a BER of 10-9. The attenuation of the 550 m GI-POF was 24.0 dB. Degradation in the order of 4.5 dB was observed in the receiver sensitivity (see Fig. 3), attributed mainly to multimode dispersion.

Figure 4: Experimental set-up for three channel WDM transmission over a link of GI PF-POF.

In the 1310 nm experiment (solid lines in Fig. 3), the average output power of the DFB laser was 0.4 dBm and the sensitivity of the receiver was -28.4 dBm at 2.5 Gbit/s for a BER level of 10-9. The attenuation of the 550 m GI-POF was 16.3 dB at 1310 nm. A 4.4 dB receiver sensitivity degradation was observed (see Fig. 3), due mainly to multimode dispersion of the fiber. The modulated spectral width of the light source was smaller than 1 nm for the 840 nm VCSEL and smaller than 0.1 nm for the 1310 nm DFB laser. These small values certainly minimized the effect of the material dispersion of the fiber. The dispersion was further avoided by the launching conditions of our experiments. In the case of the 1300 nm experiments, the SMF pigtail of the laser source was butt jointed to the GI-POF exciting only a few modes. In the case of the 840 nm experiment, also a few modes were excited because the light beam launched into the fiber was nearly parallel, meaning that the numerical aperture was not overfilled. So, the fiber exhibited less modal dispersion because the number of propagated modes was less than those than can be excited under overfilled launch conditions.

Wavelength division multiplexing transmission

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Perfluorinated polymer fiber has a low loss wavelength region ranging from 650 nm to 1300 nm, allowing for WDM transmission of several data channels. To demonstrate WDM transmission over POF the experimental set-up shown in Fig. 4 has been used. A demultiplexer for splitting up the wavelengths operating at 645 nm, 840 nm and 1310 nm has been realized with planar interference filters [11]. The measured insertion losses from GI PF-POF input to the photodetectors for all the three wavelengths were smaller than 1.6 dB. Crosstalk levels smaller than -30 dB were measured for all the three wavelengths. The demultiplexer was used for the following WDM transmission trials.

a) WDM transmission of three channels, operating at 2.5 Gbit/s over 200 m GI PF-POF. A block diagram of the set-up is shown in Fig. 4. For this experiment, the transmitters and receivers described in the previous single channel trial have been used. The multiplexing of channels has been achieved by butt-joining the fibers from the light sources to the POF sample.

b) WDM transmission of two channels operating at 2.5 Gbit/s, using the wavelengths 840 nm and 1310 nm over 328 m (one piece) of GI PF-POF. Because the fiber sample used had an attenuation of more than 100 dB/km at 640 nm, this wavelength could not be used for data transmission.

c) WDM transmission of two data channels operating at 2.5 Gbit/s, using the wavelengths 840 nm and 1310 nm over 456 m (two pieces of fiber, 328 m and 128 m long, respectively) of PF GI-POF. The bit-error rate performance has been measured to be less than 5x10-11 for the 840 nm and 1x10-11 for the 1300nm wavelength. In this experiment, a multimode silica based multiplexer has been used instead of butt-joining the pigtail fibers of the sources to the POF sample like it was done in the previous WDM experiments. This trial achieved a bit-rate distance product of 2.28 Gbit/s km.

The above experiments have shown that higher transmission capacity can be achieved in POF links by using WDM transmission. The wide low attenuation spectral window of PF polymer fiber allows for the use of available glass fiber communication laser sources operating for instance at 650nm, 850 nm and 1310 nm wavelengths. However, for POF WDM transmission to become an attractive transmission technology, low cost, reliable and compact WDM (de)multiplexer modules should become available.

6 Standardization

In this section we report on standardization activities regarding the use of POF for data transmission. The automotive industry in Europe has introduced polymer fiber for the physical layer of optical data buses. The development of a standard for a multimedia network protocol and a networks model is the focus of the media oriented systems transport (MOST) cooperation effort of more than 60 companies related to the automotive branch. The MOST data bus allows for transmission of data at a rate of 25 Mbit/s with optimized operation for compressed video transmission. The MOST standard is well developed and it is expected to be implemented by several car manufactures in the near future. For information on this standard the reader is referred to the MOST homepage http://www.mostcooperation.com. While MOST is a well consolidated European initiative, in the US and Japan, work is in progress to develop a new IEEE 1394 standard for autos that will operate at 400 Mbps. The automotive working group (AuWG) within the 1394 Trade Association pursues this activity,

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which is backed by the US and Japanese auto manufacturers. For information on the 1394TA AuWG see the groups homepage http://www.1394TA.com.

In the area of datacom applications POF has been introduced for ATM transmission. The ATM forum has developed specifications describing the physical medium dependent (PMD) sublayer for a 155.52 Mbps private user network interface (UNI) over plastic optical fiber[12]. The Japanese Standard Association (http://www.jeita.or.jp) is promoting work on the specifications for a PMD layer at S400 based on wide bandwidth POF for the IEEE 1394 –1995 and IEEE 1394a-2000. These standards focus on multimedia applications in in-home networks. Specifications are being proposed both, for the wide bandwidth POF interface and for small optical connectors. For example, parameters for the core and fiber diameter of a GI PMMA-POF have been tentatively fixed to be 500 and 750 microns, respectively [13]. The German Association of Engineers (VDI/VDE) is currently developing guidelines on testing of polymer fibers [14]. These guidelines aim to harmonize procedures for testing and measuring POF characteristics, allowing for comparability, reproducibility and traceability of measuring results. POF technology is also being considered for control and sensor applications in automobiles and for avionic communication links. We can conclude that there is a growing interest for developing standards for POF as a medium for data transmission in several areas like the automotive industry and the domestic and LAN networks. Well define standards are essential for promoting the acceptance of POF in the datacom market.

7 Potentials

Polymer optical fiber technology has reached a level of development where it can successfully replace copper based technology and multimode glass fiber for data transmission in short distance link applications such as in the office, inhome and LAN scenarios. Transmission of 10 Gbit/s data over 100 m and transmission of 1.25 Gbit/s Ethernet over ca 1 km have been experimentally demonstrated [11]. Perfluorinated polymer fiber is forecasted to be able to support bit-rate distance products in the order of 10 Gbit/s.km[1]. Short distance communications system like inhome network and office LANs represent a unique opportunity for deployment of POF based systems. POF based systems offer larger bandwidth, higher flexibility and are easier to install and handle than their copper and glass based counterparts. Moreover, POF technology presents lower price and simplicity; related mainly to its prospect of using cheap connectors and easiness of termination and maintenance. It should be noted that available light sources for glass fiber based systems can be used with PF POF systems. The same is true of connectors as in the case of Gigabit Ethernet equipment.

Feasibility of polymer fiber data networks has not only been demonstrated in laboratory trials but also in model gigabit LAN networks. Keio University of Japan has demonstrated a gigabit POF based LAN for Internet access. This University is also developing a POF based campus network and a high speed GI POF network[1]. At the Eindhoven University of Technology a POF based wireless LAN network has been developed to provide Internet access as well as for wireless connectivity of students laptops in an interactive classroom. These network demonstrators show the maturity of POF technology for data transmission. However, for POF technology to be competitive in the customer's premises it will have to operate with low cost components. These include low cost light sources, low cost receiver modules and low cost WDM devices. Light sources based on VCSELs are a promising solution. Recently, VCSEL based transceivers for PF GI-POF systems operating at speeds up to 3.2 Gbps have been demonstrated [10]. Optical connectors for GI PF-POF are also being developed [8]. These

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connectors are reported to show good characteristics such as reliability, durability and simplicity and are well suited for use in POF based LAN and home networks. We can conclude that POF technology is experiencing rapid development towards a mature solution for data transmission at short haul communications. Standard activities on POF transmission and technology are favoring this trend and its foreseen that in the near future POF will be deployed in office environments and in the customer's premises. Apart from the promising prospects of POF for data transmission, the authors would like to highlight the innovative research efforts toward a POF based optical fiber amplifier and the fabrication of polymer photonic crystal fiber [15-17]. The abovementioned POF based devices may significantly extend the potential of (polymer) optical fiber communication systems.

8 Conclusions

Polymer optical fiber is a promising technology for data transmission in short-haul communications systems such as office LANs and inhome networks. Compared to copper and multimode glass fiber based technology, POF is superior in simplicity, transmission bandwidth offered, flexibility, easiness of installation and handling, which leads lower costs. POF also guarantees electromagnetic immunity. In comparison to single mode glass fiber POF technology has inferior bandwidth and attenuation characteristics, however, POF has lower costs due to its simplicity, easiness of handling and termination and the possibility of adopting low cost connectors. POF technology is particularly suitable for applications in inhome networks (for example, 1394 networking) and office LANs. At present, POF is adopted for low bit rate optical data links in the automotive industry.

The transmission capacity of polymer fiber based systems is increasing rapidly. At bit rates of 2.5 Gbit/s, system spans of 300 m at 645 nm wavelength and 550 m at 840 nm and 1310 nm wavelength have been achieved using GI PF-POF. Higher transmission capacities have been reached by using WDM transmission. For instance, 3 channels x 2.5 Gbit/s GI-POF WDM transmission over 200 m has been reported. A WDM transmission experiment over 456 m of PF GI-POF with a record bit rate-distance product of 2.28 Gbit/s km has also been reported. Transmission of 11 Gbit/s over 100 m of PF POF has been demonstrated. POF has been shown to support transport of 1.25 Gigabit Ethernet over ca 1 km of PF POF [18]. These experimental results clearly show the applicability of polymer optical fiber for broadband applications at the customer premises and local area networks.

POF transmission technology has developed and matured enough to successfully replace copper and glass fiber as the transmission medium for short haul communication systems. High capacity networking using POF has been demonstrated not only in laboratory trials but also in model gigabit LAN networks and in wireless POF based networks for Internet access. Active efforts are being made by standardization bodies to develop guidelines for POF based physical medium; for instance for the 1394 standard. Since June 2000 PF GI-POF has been commercially available in the form of a two-fiber cable [3]. Connector technology and transceivers modules for LAN and in-home networking are also being developed. POF technology can support transmission of multimedia applications with data rates up to 10 Gbps over 100–1000 meters long links. The challenge remains in bringing POF technology (transceivers, connectors, etc.) to a competitive price and performance level for its introduction at the customer's premises.

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[10] Y-S. Lin, C-H. Chang, K-J. Chen, F-H Hou, and C.C.C. Wu, "POF Transceiver Solution Based on Short Wavelength VCSEL and GaAs PIN Components", Proceedings of the 10th

Plastic Optical Fibers Conference, Amsterdam, September 27-30, pp. 97-104, 2001;

[11] H.P.A. vd Boom, W. Li, P.K. van Bennekom, I. Tafur Monroy and G. D. Khoe "High Capacity Transmission over Polymer Optical Fiber", IEEE Journal on Selected Topics in Quantum Electronics, Vol. 7, No.3 May/June, pp. 461-479, 2001 and references therein.

[12] The ATM Forum, "155 Mb/s Plastic Optical Fiber and Hard Polymer Clad Fiber PMD Specification" version 1.1. AF-PHY-0079.001. January 1999.

[13] K. Watanabe, S. Morikura, "POF Standardization Activity of JEITA –Report from Japan", Proceedings of the 10th Plastic Optical Fibers Conference, Amsterdam, September 27-30, pp. 17-22, 2001.

[14] W. Daum, M. Hein, and O. Ziemann, "The new VDI/VDE Guideline on Testing Plastic Optical Fiber", Proceedings of the 10th Plastic Optical Fibers Conference, Amsterdam, September 27-30, pp. 31-38, 2001.

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[15] Choi, D. Y. Kim, U.C. Peak, "Fabrication and Properties of Polymer Photonic Crystal Fibers", Proceedings of the 10th Plastic Optical Fibers Conference, Amsterdam, September 27-30, pp. 355-360, 2001.

[16] M.A. van Eijkelenborg, et.al., " Microstructured polymer optical fiber", Optics express, vol.9, No.7, pp.319-327, 2001.

[17] K. Kuriki, et al., "Fabrication and optical properties of neodymium-, praseodymium- and erbium-chelates-doped plastic optical fibres", Electronic Letters, vol.37, no.7; 29 March 2001; p.415-17.

[18] H.P.A. vd Boom, T. Onishi, T. Tsukamoto, P.K. Bennekom, L.J.P. Niessen, G.D. Khoe, A.M.J. Koonen, "Gigabit Ethernet Transmission over nearly 1 km GI-POF using an 840 nm VCSEL and a Silicon APD", Proceedings of the 10th Plastic Optical Fibers Conference, Amsterdam, September 27-30, pp. 207-211, 2001.

[19] G. Keiser, Optical Fiber Communications, third edition, chapter 5, McGraw-Hill, 2000.

[20] Ref. On modal noise elimination. [Graded-Index Plastic Optical Fibers exceeding 10 Gigabit Transmission rate, Ishigure and Koike

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