High-bandwidth graded-index polymer optical fiber with high-temperature stability

A newly developed graded-index polymer optical fiber (GI-POF) with high-temperature and high-humidity stability was proposed. As it was found that the high numerical aperture and high glass transition temperature (T/sub g/) at the core center of the GI-POF were key issues to achieve both high-temperature and humidity stability, a partially fluorinated polymer material was adopted to obtain both characteristics in the GI-POF. The newly developed GI-POF had low-loss (140 dB/km at 650-nm wavelength), high-bandwidth (higher than 1 GHz for 100 m transmission), high-temperature and humidity stability at 70/spl deg/C, 80% relative humidity (R.H.) and low bending loss.     

Large-core, high-bandwidth polymer optical fiber for near infrareduse

High bandwidth (more than 500 MHz·km) graded-index polymer optical fiber (GI POF) for near infra-red use was successfully fabricated by using partially fluorinated acrylate polymer. Since only three carbon-hydrogen bonds exist in a monomer unit, an absorption loss due to the stretching vibration of the carbon-hydrogen bond was remarkably reduced compared with the conventional POF's. The attenuation of the GI POF at 780-nm wavelength was 135 dB/km, which is much lower than that of the PMMA core POF (800 dB/km). The fluorinated polymer-based GI POF is satisfying a significant segment of high-speed multimedia network applications     

Single-Mode Perfluorinated Polymer Optical Fibers With Refractive Index of 1.34 for Biomedical Applications

We demonstrate a technique for the fabrication of single-mode perfluorinated polymer optical fiber (PPOF). The PPOF preform is composed of poly-methyl-methacrylate (PMMA)-based outer cladding and a graded-index multimode PPOF as the core. A photosensitive graded-index single-mode PPOF with a core diameter of about 6.6 $ mu{hbox {m}}$ and cladding diameter of 400 $ mu{hbox {m}}$ was fabricated. The fiber has a cutoff wavelength of 854 nm and exhibits single-mode characteristics at wavelengths of 1310 and 1550 nm. The transmission loss is less than 0.2 dB/m in the wavelength range of 1410–1540 nm and less than 0.5 dB/m for wavelengths up to 1610 nm, significantly less than the typical transmission loss of $sim$100 dB/m for PMMA fiber. Another important feature of the PPOF is its low refractive index of 1.34, close to aqueous solution of biomaterials, permitting strong optical coupling for biomedical applications.      

Proton implanted VCSEL's for 3 Gb/s data links

Transverse single-mode and multimode intensity modulated butt-coupled InGaAs vertical cavity surface emitting lasers (VCSEL)s are investigated as a light source for optical fiber communication systems. Data transmission at 3 Gb/s with a bit error rate (BER) of less than 10 ^-11 is reported for both 4.3 km of standard fiber, as well as 0.5 km of multimode graded-index fiber, 10-μm active diameter single-mode VCSELs are shown to have lower mode competition noise requiring 3 dB and 6 dB less power at the front end receiver at a BER of 10^-11 compared to 19-μm and 50-μm active diameter devices, respectively. In data transmission with multimode VCSELs, the dispersion penalty is lower than for single-mode sources since the noise at the receiver is mainly determined by transmitter-mode competition noise     

Resin selection and high-speed coating of optical fibers withUV-curable materials

As a result of the curing properties of UV-curable resins, a selection criterion for UV-curable resins for high-speed fiber coating is proposed. The method is based on specifying two parameters of a UV-curable resin, which designate the Yong's modulus of cured resin. The method was used to coat graded-index fibers with the selected resins and it was demonstrated that the optical loss changes due to the coating process are small. The change of the fiber ribbon was within 0.1 dB/km under temperature changes between -40 °C and +60 °C     

Optimum profile parameter on graded-index optical fibre at 1.27 ?m wavelength

The optimum profile parameter on germanium phosphosilicate graded-index optical fibres at 1.27 ?m wavelength is examined experimentally and is found to be 1.88 ± 0.01. Graded-index optical fibres that simultaneously possess high transmission bandwidth (in excess of 1 GHz km) and attenuation below 1 dB/km are obtained.     

Design of Low-Loss Graded-Index Plastic Optical Fiber Based on Partially Fluorinated Methacrylate Polymer

As a promising candidate of optical home network, a novel Gigabit Ethernet prepared by inexpensive partially fluorinated polymer-based graded-index plastic optical fiber (GI POF) was proposed. Poly (2,2,2-trifluoroethyl methacrylate) (P3FMA) was selected as a base material for the GI POF because of its high transparency, low material dispersion, and low cost. The transmission characteristics were investigated, and it was clarified that the newly developed GI POF has low-loss (71 dB/km at 650 nm), high humidity stability, and high-bandwidth (4.86 GHz for 50-m transmission) property. Moreover, 1.25-Gbps data transmission over 50 m was demonstrated by P3FMA-based GI POF.      

Mode coupling at arc-fusion splices in graded-index fibers

Mode coupling at an arc-fusion splice has been investigated theoretically and experimentally. It has been certified experimentally that fiber parameters change at an arc-fusion splice. A mode transfer matrix has been derived which describes mode coupling at splices with fiber parameter changes along the fiber axis. The mode-coupling effects on the frequency response of spliced graded-index fibers have been investigated. Length dependence of 3 dB bandwidth has been measured for 10 km long graded-index fiber both with and without a splice. It has been clarified that the mode-coupling effect at the splice broadens the 3 dB bandwidth by 10 percent in the long fiber link in comparison with that for the fiber without a splice.     

Analysis of graded-index polymer optical fiber link performance under fiber bending

Bending effects on bandwidth and loss of a graded-index polymer optical fiber (GI POF) were investigated, and those influences on the optical link performance were discussed simultaneously for the first time. The numerical apertures (NAs) of the GI POFs were deliberately varied from 0.154 to 0.292. A bending radius larger than 10 mm induced little mode coupling and little change in the bandwidth of the GI POF. A bending radius smaller than 10 mm caused degradation in the bandwidths of the higher NA GI POFs. On the other hand, in the lower NA GI POFs, even more severe bending could cause little change in their bandwidths. Thus, the lower NA GI POF seemed preferable in suppressing the bandwidth change. However, the higher NA GI POF exhibited the lower bending loss. The preferable NAs for both characteristics were completely opposite. Moreover, the bending loss under underfilled launch (UFL) could be lower than that under overfilled launch (OFL). On the other hand, the bending loss was equivalent to the bandwidth degradation in view of the link power penalty. Therefore, the bandwidth change and loss caused by the bending were the critical factors to optimize the optical link considering the link power budget. The high-NA GI POF with almost ideal refractive-index profile could provide stable high performance in overgigabit communication even under any bending conditions.     

Intensity noise of semiconductor laser diodes in fiber optic analog video transmission

This paper presents an investigation of the effects of laser diode noise on analog video transmission in the HF and VHF bands, which resulted in the development of several designs of graded-index multimode fiber systems that can ignore reflection induced laser noise. The contents of the investigation include: 1) The evaluation of intrinsic laser noise of various laser structures and the evaluation of modulation effects on laser diode noise characteristics. It was found that the relative intensity noise (RIN) is less than -145 ∼ -150 [dB/Hz] when the modulation factor is less than 0.7 for index-guide mode stabilized lasers; 2) The quantitative evaluation of reflected laser beam effects on laser noise characteristics. The maximum laser-coupled reflected optical power that does not increase laser noise was determined as-65 ∼ -73 dB or less depending on the kind of laser structure; and 3) The evaluation of optical power reflected back into the laser in graded-index multimode fiber systems.     

High-Speed CMI Optical Intraoffice Transmission System: Design and Performance

This paper presents the design and performance features of a successfully developed optical intraoffice transmission system operating at 100-400 Mbits/s. The keys to the commercial realization of this simple, highly reliable, and low-cost system are the employment of the 1.3 μm LED and graded-index multimode fiber. Additionally important, the system makes use of coded mark inversion (CMI) coding to ensure bit sequence independence (BSI) and good error-monitoring capability. Experimental results have clarified the optimum bandwidth of the low-pass filter at the receiver end and the commercially attainable transmission distance. Furthermore, an available system gain of 15.4 dB is demonstrated through 400 Mbit/s transmission experiments. This value enables transmission over distances in excess of 4 km through multimode fiber (900 MHzcdotpkm, 0.8 dB/km).     

Microoptic grating multiplexers and optical isolators for fiber-optic communications

As new optical devices for increasing further the utility of and to expand the application of fiber-optic communications, grating multiplexers and isolators have been developed for 0.8 μm band employing microoptic approach. The development of these devices is the subject of this paper. The devices have desirable features of small size, compactness, high optical performances, and high reliability. The grating multiplexer consists of a graded-index rod, a blazed reflection grating replicated onto the graded-index rod slanting facet or a wedge facet, and an input-output fiber array. Simple calculations have been done to determine necessary element parameters for a given channel spacing. Experimental results are presented for five-channel multiplexers devised using a SELFOC^®lens. Around 3 dB insertion loss and less than -30 dB crosstalk have been obtained for about 35 nm channel spacing in overall device size of18 times 13 times 50mm. Faraday rotation optical isolators for 0.8 μm band have been miniaturized by employing an efficient paramagnetic glass Faraday rotator, a magnet with a through hole and a folded optics in the Faraday rotator. The path number in the folded optics has been optimized in terms of trading-off between the magnet size and the insertion loss. A 0.9 dB insertion loss including fiber coupling loss and 36 dB isolation have been obtained in overall device size of24 times 24.5 times 42mm. Results on the temperature and wavelength dependence of the isolation are also presented. In addition, fundamental properties of optical circulators for 0.8 μm band and optical isolators and circulators both for 1.3 μm band, developed as extended modifications of the optical isolators for 0.8 μm band, are briefly described.     

Wide-beam propagating fiber for inline optical components

A new technique is proposed for integration of bulky optical components by means of a specific graded-index fiber in which the fundamental mode has a large mode-field diameter (MFD). A wide-beam propagating (WBP) fiber with the field diameter as large as 60 /spl mu/m was successfully fabricated, which will enable bulky optical components that have no wave-guiding structures to be embedded into a fiber circuit without any lenses. It was confirmed that a 5-mm-thick silicon plate, for example, can be integrated into the fiber with a loss of less than 1 dB. A hemispherically ended WPB fiber for much longer bulky components is also proposed.     

基于弯曲损耗的光纤温度传感器

为了推导多模光纤弯曲损耗与弯曲半径、环境温度的关系,采用了WKB法求解非均匀直光纤的传播模数,并将弯曲光纤的有效折射率、弯曲光纤截止传播常数和光纤的热光效应同时引入到非均匀直光纤有效传播模数中。利用多模光纤进行实验验证,研制出测温灵敏度为0.1/℃、测温范围为10℃～70℃的光纤温度传感器。结果表明,弯曲损耗随弯曲半径的增大而减小,随环境温度的升高而减小,可以利用弯曲损耗测量环境温度。     

Design of a submarine optical-fiber cable using graded-index multimode fibers

This paper describes a designing method for a submarine optical-fiber cable unit consisting of graded-index multimode optical fiber. It has been assumed that excess losses inherent in cable manufacture are dominantly dependant on the lateral force yielded by wrapping tape. The excess losses have theoretically been derived and expressed by optical-fiber unit parameters. Through theoretical and experimental results, the suitable fiber-unit parameters have been given. Based on these investigations, two cable pieces have been fabricated. Excess losses of the cable, which are made with the suitable unit parameters, have been only 0.01 dB/km. This fact may prove the design suitability.     

低耦合损耗的光电混合光纤旋转连接器

设计了一种光电混合光纤旋转连接器,能实现相对旋转的光信号在较大对准误差范围内低损耗连接.旋转状态下的自聚焦透镜准直光纤输出的光信号,并由PIN光电探测器将其转换为电信号,冉由激光器根据电信号再生出原始光信号继续在光纤通讯系统中传输.该光电混合光纤旋转连接器在离轴偏移量至520μm或对准倾斜角至0.5°时的附加耦合损耗为0.3 dB,而采用双自聚焦透镜的光纤旋转连接器要获得小于3 dB的插入损耗,其离轴偏移或倾斜角度必须小于100 μm和0.10°相比之下,本文设计的光纤旋转连接器能降低系统对机械加上及装配精度的要求,具有较高的实用价值.     

Optimum index profile of the perfluorinated polymer-based GIpolymer optical fiber and its dispersion properties

The significant advantages in bandwidth and low material dispersion of perfluorinated (PF) polymer-based graded-index polymer optical fiber (GI POF) are theoretically and experimentally reported for the first time. It is confirmed that the low attenuation and low material dispersion of the PF polymer enables 1 Gb/s km and 10 Gb/s km transmission at 0.85-μm and 1.3-μm wavelengths, respectively. The PF polymer-based CI POF has very low material dispersion (0.0055 ns/nm·km at 0.85 μm), compared with those of the conventional PMMA-based POF and of multimode silica fiber (0.0084 ns/nm km at 0.85 μm). Since the PF polymer-based GI POF has low attenuation from the visible to near infrared region, not only the 0.65-μm wavelength which is in the low attenuation window of the PMMA-based GI POF, but other wavelengths such as 0.85-μm or 1.3-μm etc. can be adopted for the transmission wavelength. It is clarified in this paper that the wavelength dependence of the optimum index profile shape of the PF polymer-based GI POF is very small, compared to the optimum index profile shape of the silica-based multimode fiber. As a result, the PF polymer-based GI POF has greater tolerance in index profile variation for higher speed transmission than multimode silica fiber. The impulse response function of the PF polymer-based GI POF was accurately analyzed from the measured refractive index profile using a Wentzel, Kramers, Brillouin (WKB) numerical computation method. By considering all dispersion factors involving the profile dispersion, predicted bandwidth characteristic of the PF polymer-based GI POF agreed well with that experimentally measured     

Intrusion-alarmed fiber optic communication link using a planarwaveguide bimodal launcher

This paper summarizes the results of our study of a point-to-point, intrusion-alarmed, graded-index, multimode optical fiber communication system. In this intrusion-alarmed system, data light is transmitted in the lowest order modes of a graded-index multimode fiber and intrusion alarm monitor light is simultaneously transmitted in high-order modes. An attempted intrusion to extract data light by bending the fiber results in attenuation of the monitor light in high-order modes, thereby sounding an alarm at the receiver. However, the data light in the fundamental mode, or in the lowest order modes, propagates along or near the fiber axis where the refractive index is highest and is exceptionally difficult to extract from the fiber. Even for severe bending of the fiber, light in the lowest order modes remains trapped in a set of lowest order modes. Additional benefits of data light transmitted in the lowest order modes are capabilities for wider bandwidths and lower modal noise. The performance of four fabricated planar waveguide bimodal launchers for simultaneously launching data light into the fundamental mode, or into the lowest order modes, and monitor fight into high-order modes of graded-index multimode fiber is described. The configuration, construction, and performance of a laboratory prototype alarmed system are described     

An effective nonreciprocal circuit for semiconductor laser-to-optical-fiber coupling using a YIG sphere

A practical nonreciprocal optical circuit for laser-diode (LD)-to-optical-fiber coupling in the 1.3-μm wavelength region is described. It consists of a yttrium iron garnet- (YIG) sphere graded-index (GRIN) rod lens and a polarizer. The YIG sphere can function not only as a Faraday rotator but also as an effective coupling lens. High coupling efficiency of more than -5 dB for a single-mode fiber, and more than -2 dB for a multimode fiber, is easily achievable. Alignment sensitivities and coupling characteristics of the proposed circuit are also discussed theoretically and experimentally. The increase in LD relative intensity noise (RIN), caused by light injected into the LD, is estimated using the reciprocal characteristics of LD-to-single-mode-fiber coupling. By comparing the LD-RIN increase in the proposed non-reciprocal circuit with that of the reciprocal, high isolation of about 32 dB is confirmed. The fact that reflected light from the proposed circuit has little influence on LD characteristics is also clarified.     

Design and characteristics of a branching component for bunched optical fiber using two graded-index rod lenses

An optical branching component is proposed for coupling bunched optical fiber to mono-core optical fibers and the component loss and crosstalk characteristics are investigated. The component is constructed with two graded-index (GRIN) rod lenses for matching different parameters between bunched and mono-core optical fibers. The method of analyzing mismatching and misalignment losses is based on geometrical optics. Measured losses are found to be in agreement with the calculated results and demonstrate that bunched optical fibers can be branched with low loss. Crosstalk measurements show that crosstalk attenuation greater than 30 dB can be easily maintained in the component.