Graded-index Plastic Optical Fiber Research Articles

Significantly Robust Data Transmission by Ballpoint-Pen Interconnect for Graded-Index Plastic Optical Fiber

We have developed a novel optical interconnect for graded-index plastic optical fibers based on the use of ballpoint-pen connectors, where ball lenses are precisely mounted on fiber end faces by a simple and low-cost ballpoint-pen production technology. This report demonstrates that the ballpoint-pen interconnect allows us for significantly robust data transmission with sufficient misalignment tolerance and mating durability for consumer applications, where very short optical fibers are frequently connected and disconnected to the consumer electronics in a manner similar to metal cables. In the ballpoint-pen interconnect, power penalties are barely affected even by misalignments with a lateral offset of 50 μm or a connector separation of 1.0 mm, allowing for optical fiber connections without the requirements of precise alignment or high manufacturing accuracy. Moreover, it is suggested that modal noises due to dusts and scratches on fiber end-faces are generated for conventional butt-coupling based on physical contact in applications that require frequent connection and disconnection of optical fibers. This modal noise generation can be prevented using nonphysical contacts with the ballpoint-pen connectors. We achieve high-speed data transmission that is barely influenced by 2500 mating cycles. These results suggest that the ballpoint-pen interconnect allows us for consumer-friendly optical fiber connections without the requirement of any cleanings in a manner similar to electrical interconnect.

MIMO-enabled integrated MGDM–WDM distributed antenna system architecture based on plastic optical fibers for millimeter-wave communication

Design of a low-cost fiber–wireless communication architecture is desirable by network operators. Therefore, we demonstrate the transmission of $$2 \times 2$$ MIMO spatial streams, each having 2 Gbps DPSK signal to two different radio access units (RAUs) in a distributed antenna system architecture. The proposed architecture employs mode group division multiplexing in combination with wavelength division multiplexing to transport RF DPSK signals centered at 10 GHz. The RF signals are used to modulate optical carriers that are centered at 1300 nm and transmitted toward the RAUs over perfluorinated graded-index plastic optical fiber. Heterodyne detection is performed at the RAUs to transmit mm-wave signals at 60 GHz to the end users. Furthermore, wireline access is also achieved at each RAU to support simplex services. A cost-efficient multiple wavelength source is generated from a single laser by employing a dual-drive Mach–Zehnder modulator. An increase in multiplexing gain is achieved using the two LP modes, LP01 and LP11, of each generated wavelength. The proposed architecture gives acceptable BER results for practical implementation.

An analysis of W-shaped plastic optical fibers by WKB approximation

The graded-index plastic optical fiber, because of its relatively large bandwidth and core diameter, is the type of fiber that is used in a majority of the fiber optic systems in existence today. Especially the type of optical fiber known as the W-fiber has some desirable properties and unique characteristics not found in matched-cladding fibers. In this work, by Wentzel–Kramers–Brillouin (WKB) method, the total number of modes of the graded-index W-shaped plastic optical fiber is theoretically reviewed. The obtained formula for the total number of modes of W-shaped optical fibers arises from an approximation of the WKB integral, which preserves the general validity requirements of the method. Also, by assumption that all modes were excited uniformly, the computational analyses investigating near- and far-field power distribution in W-shaped plastic optical fibers was carried out.

LTE‐A compliant multi‐band radio and gigabit/s baseband transmission over 50 m of 1 mm core diameter GI‐POF for in‐home networks

The transmission of multiple standard-compliant long-term evolution advance (LTE-A) bands together with a 4-pulse amplitude modulation (PAM) baseband signal over 50-m-long 1 mm core diameter poly- methyl methacrylate graded-index plastic optical fibre is demonstrated. Transmission of eight LTE-A 64-QAM bands and a 1.2 Gbit/s 4-PAM baseband signal over the fibre was achieved resulting in an error vector magnitude <8% and pre-forward error correction (FEC) BER < 10−3, respectively.

High-Speed Graded-Index Plastic Optical Fibers and Their Simple Interconnects for 4K/8K Video Transmission

We developed a consumer-friendly interface graded-index plastic optical fiber (GI POF) cable with the ballpoint-pen interconnects for uncompressed 4K/8K video transmission of 120 Gb/s. Since the material dispersion of perfluorinated GI POF is smaller than that of silica multimode fiber (MMF) at 850-nm wavelength, the bandwidth achieved by GI POF is higher than that of silica MMF. Moreover, it is confirmed that by using GI POF with larger-scale microscopic polymer heterogeneities, serious noise problems observed in silica MMF are much improved by GI POF, which is achieved by resulting stronger mode coupling. This suggests that thinner 4K/8K cables can be feasible by using multilevel transmission through the low-noise GI POFs. The high-speed and low-noise GI POF is paving the way for consumer applications of 4K/8K optical interface toward the 2020 Tokyo Olympics and Paralympics.

Misalignment Tolerance of Pluggable Ballpoint-Pen Interconnect of Graded-Index Plastic Optical Fiber for 4K/8K UHD Display

Misalignment Tolerance of Pluggable Ballpoint-Pen Interconnect of Graded-Index Plastic Optical Fiber for 4K/8K UHD Display

Effects of para-fluorine substituent of polystyrene on gradient-index fiber-optic properties

To study the effects of fluorine substituent of polystyrene (PSt) on gradient-index fiber-optic properties, a poly(para-fluorostyrene) (P(p-FSt))-based graded-index plastic optical fiber (GI POF) is fabricated, and its properties are compared with those of a PSt-based GI POF. The para-fluorine substitution positively affects the glass transition temperature (Tg) of the core, wavelength dispersion of the optimum refractive index profile, bandwidth, and attenuation. The core Tg of the P(p-FSt)-based GI POF is 88°C, which is higher than that of the PSt-based GI POF by 9°C when both fibers have an identical numerical aperture (NA=0.2). The optimum refractive index profile coefficient for the P(p-FSt)-based GI POF varies from 2.2 to 2.1 in the 600–800nm range, whereas that for the PSt-based GI POF varies from 2.6 to 2.3 in the same wavelength region. The bandwidth of the P(p-FSt)-based GI POF is intrinsically higher than that of PSt-based GI POF. Moreover, the fiber attenuation of the P(p-FSt)-based GI POF was significantly smaller than that of the PSt-based GI POF over the source wavelength range. Our study demonstrates that P(p-FSt) has favorable properties as a GI POF base material.

Ultra-Sensitive Strain and Temperature Sensing Based on Modal Interference in Perfluorinated Polymer Optical Fibers

We implement the strain and temperature sensors based on multimode interference in perfluorinated (PF) graded-index (GI) plastic optical fibers, and investigate their sensing performance at 1300 nm. We obtain strain and temperature sensitivities of -112 pm/μe/m and +49.8 nm/°C/m, the absolute value of which are 12.9 and over 1800 times as large as those in silica GI multimode fibers, respectively. These ultra-high strain and temperature sensitivities probably originate from the unique core material, i.e., PF polymer.

Effect of cladding layer glass transition temperature on thermal resistance of graded-index plastic optical fibers

The long-term thermal stability of the attenuation of graded-index plastic optical fibers is strongly dependent on whether the glass transition temperature (Tg) of the cladding layer is higher than the environmental temperature. When fibers are exposed to temperatures higher than both the core and cladding Tg values, the core-cladding boundary fluctuates spatially and scatters light. However, our study indicates that the core is not necessarily required to be in a glassy state to maintain a flat, smooth interface as long as the cladding is in a glassy state.

Refractive index and strain sensing using inline Mach–Zehnder interferometer comprising perfluorinated graded-index plastic optical fiber

This paper details the fabrication and performance evaluation of an inline Mach–Zehnder interferometer (MZI) consisting of a perfluorinated graded-index plastic optical fiber fabricated via a heat-and-pull tapering technique. This MZI exhibits interference fringes that are sufficiently sharp for usage as refractive-index (RI) and strain sensors. These interference fringes shift linearly with the RI of the surrounding medium, with a proportionality constant of 3.44nm/RI unit. The measured strain sensitivity of 0.2pm/μɛ suggests that the MZI may be viable for strain-sensing applications.

DVB-S2 and DVB-T RF Transmission in 1-mm GI-POF System

An optical system for the transmission of digital video broadcasting (DVB) signals is proposed and experimentally demonstrated. The transmission media comprises 1-mm diameter graded-index plastic optical fiber (GI-POF) with a relatively high bandwidth. The system is fully engineered using low-cost off-the-self components including a vertical-cavity surface-emitting laser, a silicon avalanche photodiode, POF connectors, and all integrated radio frequency (RF) circuitry. The RF distribution of standard DVB-satellite second generation signals in 950-2150 MHz and DVB-terrestrial signals in 470-790 MHz over 25-m GI-POF is successfully demonstrated.

Polymeric wavelength division multiplexing coupler with fiber guide and filter trench for bidirectional communication fabricated by one-step replication

We fabricated and characterized a polymeric bidirectional wavelength division multiplexing (WDM) coupler for a graded-index plastic optical fiber (GI-POF). We fabricated the device with fiber guides and a filter trench by a simple one-step soft lithography method. We evaluated the performance of the fabricated device with an optimal design structure at wavelengths of 850 and 790 nm. We determined the insertion loss, isolation, and directivity to be less than 3 dB, more than 20 dB, and more than 20 dB, respectively. We also demonstrated bidirectional communications with more than 2.5 Gbps/λ for an optical fiber length of 150 m by aligning the GI-POF in the fiber guides and inserting a WDM filter in the filter trench with passive alignment.

Reflection noise reduction effect of graded-index plastic optical fiber in multimode fiber link.

We experimentally demonstrate that a graded-index plastic optical fiber (GI POF) can significantly reduce reflection noise in a multimode fiber link with a vertical-cavity surface-emitting laser (VCSEL). By directly observing beams backreflected to the VCSEL, we show that the noise reduction effect is closely related to random mode coupling because of light scattering by microscopic heterogeneities in the GI POF core material. This suggests that intrinsic mode coupling can lower the self-coupling efficiency of the light backreflected to the VCSEL cavity through beam quality degradation. Using GI POFs, low-cost radio-over-fiber systems for indoor networks can be realized without optical isolators or fiber end-face polishing.

Evaluation of modal noise in graded-index silica and plastic optical fiber links for radio over multimode fiber systems

We have evaluated and compared modal noise induced in a graded-index silica multimode fiber (GI-MMF) link and a graded-index plastic optical fiber (GI-POF) link with the misaligned fiber connections. In radio over fiber (RoF) systems using these optical fibers, modal noise appears as unwanted amplitude modulation in the received signal, and results in degradation of the RoF transmission performance. In this work, we have evaluated the modal noise induced in GI-MMFs and GI-POFs with its same core diameter of 50 μm. Our results show that GI-POFs have an inherently higher tolerance to misaligned connection and less modal noise than GI-MMFs in terms of both the error-vector magnitude and the speckle pattern of the transmitted signals.

New insights into dopant design for graded-index plastic optical fibers for transmission at 850 nm

To develop graded-index plastic optical fibers (GI POFs) which can be utilized for transmissions at 850nm, not only do molecular vibrational absorptions of the base polymeric materials need to be considered, but also the dopants used. In this study, chlorinated aromatic dopants were synthesized and their effects on the optical and thermal properties of poly(pentafluorostyrene), which has the low-loss window at 850nm, were studied. The polymers doped with chlorinated dopants showed no absorption peak and retained the broad windows around the source wavelength. Furthermore, they showed higher glass transition temperatures when compared at similar refractive indices than the polymer doped with diphenyl sulfide, which is the most common dopant for acrylates and styrenes-based GI POFs. However, as the chlorine content per dopant molecule increased, the compatibility with the base material became worse and the doped polymer exhibited a higher attenuation due to an increment of light scattering.

Lensed plastic optical fiber employing hyperbolic end filled with high-index resin using electrostatic force

Abstract The step-index (SI) and graded-index (GI) plastic optical fibers (POFs) are strong candidates for short-distance transmission, fiber-to-the-home (FTTH) networks, automobile applications and interchip interconnections. The GI POFs which has been proven to reach distances as long as 1 km at 1.25 Gb/s has a relatively low NA. Therefore, the efficient coupling of GI POFs to the light source has become critical to the power budget in the system. Forming a lens-like structure directly on the fiber end is preferred for simplicity of fabrication and packaging, such as polishing and fusion, combing different fibers with the cascaded fiber method and hydroflouride (HF) chemical etching. These approaches are well established, but applicable only to glass. This work proposes a novel structure of a lensed plastic optical fiber (LPOF). The fabrication of the LPOF is demonstrated and the coupling efficiency exceeds 72%.

Efficient group delay averaging in graded-index plastic optical fiber with microscopic heterogeneous core

Intrinsic mode coupling in a graded-index plastic optical fiber (GI POF) is investigated using the developed coupled power theory for a GI POF with a microscopic heterogeneous core. The results showed that the intrinsic material properties can induce random power transitions between all the guided modes, whereas the structural deformation of microbending results in nearest-neighbor coupling. It was numerically demonstrated that efficient group-delay averaging due to intrinsic mode coupling brings the pronounced bandwidth enhancement in fibers with much shorter length than the case of glass multimode fibers.

In-home networks integrating high-capacity DMT data and DVB-T over large-core GI-POF

The low-cost in-home distribution of full-standard digital TV jointly with high-bitrate data using 50 m long 1 mm core diameter graded-index plastic optical fiber (GI-POF) is proposed and experimentally demonstrated. Discrete multitone (DMT) modulation is demonstrated to provide an adaptive bitrate which can spectrally coexist with digital video broadcasting-terrestrial (DVB-T) signals in 470-862 MHz. A 3 Gb/s DMT signal and two DVB-T channels are generated, transmitted and received exhibiting excellent performance.

An Integrated Long-Reach PON and GI-POF In-House Network Architecture for Hybrid CATV/OFDM Signals Transmission

We propose and demonstrate an integrated long- reach passive optical network (PON) and in-house graded-index plastic optical fiber (GI-POF) network architecture for hybrid community antenna television (CATV) and orthogonal frequency division multiplexing (OFDM) signals transmission. By reasonably multiplexing the OFDM and CATV signals into a CATV transmitter, both signals originated from a central office (CO) are successfully transmitted over a span of 60 km single mode fiber (SMF) and another span of 25 m GI-POF to consumers' devices. Although the SMF and GI-POF have different core sizes and attenuation features, no any bridge circuit or wavelength converter is utilized in the proposed architecture resulting in a transparent platform for the Internet service providers (ISPs) to directly manage their long-distance services toward suburban or rural areas. Since the optical signal generated at the CO can be transmitted straightforward to the consumers' devices, the average packet delay and packet overhead size can be greatly reduced and the quality of services (QoS) can be maintained easier. Good experimental performances of the CATV and OFDM signals transmission proof the practice and efficiency of this proposal to extend multimedia services from metro areas to suburban and rural areas.

4$\,\times\,$10 Gb/s High-Speed Link Over Thin GI 50/125 Plastic Optical Fibers and Compact Optical Sub-Assembly

We introduce an extremely thin 50/125 perfluorinated graded-index plastic optical fiber (POF) and its application in a 4×10 Gb/s optical link including our optical sub-assembly (OSA). We outline the main characteristics of the POF before the introduction of the fibers to our already established OSA is explained. Particularly low attenuation with error-free transmission down to a bending radius of 1 mm is presented in comparison to a quartz optical fiber. Furthermore eye diagrams of all four channels after 5 m over POF at 10 Gb/s are presented. Bit error rate for all channels is less than 10-12 and remains constant when another channel is being driven simultaneously.