Step-index Plastic Optical Fiber Research Articles

Coupling of Modes in Step-Index Plastic Optical Fibers by Using D-Shape Technique.

This article presents a technique for reducing the stabilization length of steady-state modes in step-index plastic optical fibers (POFs), which is significant for sensor networks, Internet of Things, signal processing, and data fusion in sensor systems. The results obtained with the com- putational tool developed suggest that the D-shape created in the POF effectively reduces the stabi- lization length of the modes and, by extension, minimizes the dispersion effects of the modes by filtering out high-order modes. Applying the analysis to commercial POFs, the authors experimen- tally verified a reduction in the stabilization length of modes from 27 to 10 m and from 20 m to 5 m. Reducing the mode stabilization length minimizes the bit error rate (BER) in short-length SI-POF- based optical links operating at 250 Mbp/s. A reduction from 7.6 × 10-7 to 3.7 × 10-10 was achieved.

Theoretical and experimental investigation of the steady-state power distribution in multimode step-index plastic optical fibers

In this work we have examined theoretically and experimentally the influence of mode coupling on steady-state distribution (SSD) in step-index plastic optical fiber (SI POF). Numerical and analytical solution of the PFE under steady-state conditions are compared to our experimental results. A numerical solution of the power flow equation (PFE) has been obtained by the explicit finite difference method (EFDM). We demonstrated that SSD in the SI POF is achieved at length of 140 m, which is much shorter length compared to the case with silica fibers. The reported results appear to be particularly important since none of the main optical properties of an optical fiber (attenuation, bandwidth) can be accurately determined until the transmitted optical power reaches its SSD, due to strong influence of mode coupling phenomena that occur during the transmission process. These results are important for employment of the SI POFs as a part of communication or sensory systems.

Bidirectional Gigabits Per Second Spatial Diversity Link Using POF for Passive Optical Front-Ends

This paper presents a novel concept for spatial diversity using plastic optical fibre (POF)-based luminaire transmission for in-home networks. We show the feasibility of an optical transmission system using POFs, acting as optical front-haul, for realizing a high capacity wireless bidirectional link aided by a spatial diversity scheme allowing user mobility around the access points. The light coming out of the 1 mm core diameter step-index POF is highly divergent and, therefore, for each POF-end an optical lens is placed to adjust the size of wireless cells, in order to allow user's mobility or to adjust the number of users served by the access points. Thus, the access points are completely passive, hence no electrical powering is needed, resulting in low maintenance. In addition, active components such as light sources and detectors can be located remotely from the access points and they are connected to each other by POFs. Futhermore, we performed optical wireless experiments with an eye-safe visible light laser and therefore our wireless link is limited to 1.2 m and 45 cm diameter of coverage areas. We obtained multi-Gbps for downlink and uplink and compared the link performance using discrete multitone, pulse amplitude modulation, and Nyquist sub-carrier modulation.

Characterization of Mach Zehnder interferometer plastic optical fiber for intensity-based temperature sensor

This paper presents characterization of optical temperature sensor using step-index plastic optical fiber (SI-POF) in intrinsic Mach Zehnder interferometer (MZI) structure. The MZI was developed by forming two tapers at several distance. By exploiting the wavelength dependency of spectrum intensity, measurement was done by using intensity based measurement at two different wavelengths. Characterizations were done to obtain the sensor performance which were sensitivity and hysteresis. The characterization was carried out by launching white LED to the sensor while the sensor was in temperature controlled-oven. The output spectrum was observed at the other sensor tip using spectrometer at various temperature which are 35°C to 85°C with increment of 10°C. It was found that the sensor has sensitivity and hysteresis of 1×10−3/°C and 1.97×10−2, respectively.

Langevin Equation Approach to Mode Coupling in Heated Step-Index Plastic Optical Fibers

The Langevin equation is used to investigate the state of mode coupling in step-index plastic optical fibers under varied temperature. The numerical integration of the Langevin equation is based on the computer-simulated Langevin force. The solution matches the experimental data reported previously. We find that elevated temperatures of plastic optical fibers are strengthening mode coupling. We show that, solving the Langevin equation (stochastic differential equation), one can treat a mode coupling in heated multimode step-index plastic optical fibers, which is a result of fiber’s intrinsic random perturbations.

SI-POF Supporting Power-Over-Fiber in Multi-Gbit/s Transmission for In-Home Networks

We propose the integration of power-over-fiber (PoF) in home networks with multi Gbit/s data transmission based on wavelength-division-multiplexing (WDM) in step-index plastic optical fibers (SI-POF). Different powering architectures are described. The efficiencies of different components are discussed to address the maximum remote energy that can be delivered. Experimental results show the ability of the system to deliver several mW of optical power with negligible data signal quality degradation and with BER of 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-10</sup> . The potential of utilizing PoF in combination with low-loss WDM-POF to optically powering multiple devices for specific in-home applications and IoT ecosystems is discussed. A PoF scalability analysis is detailed.

Characterization of Temperature Response of Asymmetric Tapered-Plastic Optical Fiber-Mach Zehnder Interferometer

Temperature measurement is important in various applications; therefore, various temperature sensors have been developed. Due to its advantages, many optical fiber-based temperature sensors have been proposed. The wavelength modulation-based optical sensor is interesting due to high accuracy. However, the complex fabrication process and high cost limit the advantages of the sensors. Therefore, we proposed a simple and low-cost Mach Zehnder interferometer (MZI) sensor using step-index plastic optical fiber (SI-POF). Performance characterization of the sensor to temperature variation is presented. The sensor consists of two tapers at several distances, forming an interferometer. The first taper was designed to be steep to allow excitation of cladding modes, while the second taper was gradual to suppress power loss. Characterizations were done in terms of sensitivity, hysteresis, and repeatability by analyzing the output spectrums recorded by the spectrometer at various environment temperatures, 35oC to 85oC, with an increment of 10oC. The results showed that the sensor has a sensitivity of 0.0431 nm/oC and a correlation coefficient of 0.9965. Hysteresis of 6.9×10-3 was observed. In terms of repeatability, the sensor shows a maximum deviation, ±3oC, which was mainly resulted from the fluctuation of the oven temperature. Despite its high deviation, the sensor has advantages of simple fabrication, low cost, robust, and low power loss, which make it a good candidate for temperature sensors.

Theoretical investigation of bending loss in step-index plastic optical fibers

Behavior of the step-index plastic optical fibers (SI POFs) is examined in a straight-curved configuration for various launching conditions and fiber curvature. This was achieved by applying the power flow equation to calculate the power distribution at the end of the straight fiber segment that precedes the curved one, allowing calculation of the power loss for the latter. We have shown that a small bend radius (r<0.04 m) and launch angles close to the critical angle should be avoided when using this type of SI POF in power delivery and communication systems. These results may be useful when choosing between various operating fiber conditions in order to prevent possibly high bending-induced losses.

Experimental Demonstration of Subband Index Techniques for &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$m$ &lt;/tex-math&gt; &lt;/inline-formula&gt;-CAP in Short-Range SI-POF Links

In this letter, novel spectrally efficient subband index (SI) techniques have been developed for multiband carrierless amplitude and phase modulation ( $m$ -CAP). The SI techniques transmit additional information bit on the index of the conventional $m$ -CAP subbands. Experimental demonstrations are performed in a short-range optical data link using step-index plastic optical fiber. The demonstrations show that the proposed techniques enable flexibility in design and significantly improve the power/spectral efficiency of the conventional $m$ -CAP.

Large-Time-Step-Based Ray-Tracing Modeling of Light Delivery in One-Sidedly Cladding-Removed Step-Index Plastic Optical Fiber under Arbitrary Weave Structure

An advanced theoretical method to simulate the light delivery in plastic optical fiber is presented. The final objective is to use “light” as a new media for information delivery in wearable computers. A large-time-step-based ray-tracing algorithm, which was improved from our previous research, was used to simulate the light vector movement in a complex weave structure efficiently. NURBS and free-form-deformation-based modeling was used to mimic the arbitrary weave structure. Experimentally, optical fibers were modified to control the direction of light emission. Particularly, half side of a cladding layer in the radial direction was selectively removed to enhance one-sided fabric light scattering. The cladding-removed plastic optical fiber was adopted in a textile weave structure, and its light scattering was measured quantitatively by varying the removal length, fiber curvature, and fabric weave patterns. To show the validity of the proposed simulation technique, twill structures with varying number of cross repeat numbers were used as a testbed. The unit number 2 was found to be the optimal structure for light emission, when a single POF was embedded in the textile. The proposed model showed the similar result with the actual light intensity measurement, with computation time not much than one second.

Enhanced bandwidth of W type plastic optical fibers designed from singly clad step index plastic optical fibers

We propose a multimode W type (doubly clad) plastic optical fiber which takes the characteristic W-shaped index profile designed from a multimode singly clad step index plastic optical fiber upon modification of the cladding layer of the latter. For different widths of the inner cladding and refractive index of the outer cladding, the bandwidth and steady-state loss are determined for such W type plastic optical fiber. We have shown that bandwidth of W type plastic optical fiber is significantly higher than the bandwidth of the original singly clad step index plastic optical fiber. The bandwidth of W type plastic optical fiber is mostly enhanced by reducing the width of its inner cladding.

Temperature insensitive low-loss optical connection for automotive gigabit plastic optical fiber communication

Step-index plastic optical fibers (SI-POFs) have already been implemented in automotive optical communication because they offer some significant advantages; they are free from electromagnetic noise and are appropriate for reliable data transmission in harsh environment applications. In current systems, an air gap exists between the fiber connections, and the gap size changes because of temperature variations. We propose and demonstrate an approach for the SI-POF in-line connection, which is targeted for automotive gigabit optical communication. We designed and fabricated an up-tapered ferrule and inserted an index matching material into the gap. By using the up-tapered ferrule, we obtained more stable insertion loss, which is proven by the heat cycle tests. By inserting the index matching material, the insertion loss becomes lower. Moreover, an encircled angular flux evaluation also confirmed that our approach does not change the modal power distribution of the fiber.

10-Gb/s Transmission Over 10-m SI-POF With &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;${M}$ &lt;/tex-math&gt; &lt;/inline-formula&gt;-PAM and Multilayer Perceptron Equalizer

We demonstrate the gigabit-per-second transmission over a step-index plastic optical fiber (SI-POF) of 10-m length with a pulse-amplitude modulation (PAM). A multilayer perceptron-based equalizer is used to mitigate an intersymbol interference and non-linearity in the system. Using this equalizer with 32-PAM, a data rate of 10 Gb/s is achieved over the 10-m SI-POF at a bit error rate of 10−2, which is below the 20% forward error correction limit.

Influence of mode coupling on three, four and five spatially multiplexed channels in multimode step-index plastic optical fibers

We investigate the influence of mode coupling on space division multiplexing capability of three multimode step-index plastic optical fibers with different strengths of mode coupling. Results show that mode coupling significantly limits the fiber length at which the space division multiplexing can be realized with a minimal crosstalk between the neighbor optical channels. Three, four and five spatially multiplexed channels in the investigated multimode step-index plastic optical fibers can be employed with a minimal crosstalk up to the fiber lengths which are about 7%, 5% and 3% of the corresponding coupling lengths (fiber length where equilibrium mode distribution is achieved), respectively. Such characterization of optical fibers should be considered in designing an optical fiber transmission system for space division multiplexing.

Performance Comparison of Equalization Techniques for SI-POF Multi-Gigabit Communication With PAM- M and Device Non-Linearities

In this paper, Gigabit per second transmission over short-range step-index plastic optical fibre (SI-POF) is implemented with multi-level pulse amplitude modulation (PAM- M ) scheme using a laser diode (LD) as the optical source. In particular, the POF channel distortion and the non-linear distortion from the LD are considered. To mitigate these distortions under various PAM- M levels, the bit error rate (BER) performances of the transversal, Volterra and multi-layer perceptron (MLP) based decision feedback equalizers are evaluated and compared. Furthermore, the inverse polynomial technique for non-linear mitigation is also considered. MLP is shown to offer the best BER performance for PAM scheme using more than eight levels especially for a system with high non-linearities. With the MLP equalizer, we record the highest data rate of 3, 7.8, and 18 Gbps for POF lengths of 60, 30, and 10 m, respectively.

Ray-Tracing-Based Modeling of Clad-Removed Step-Index Plastic Optical Fiber in Smart Textiles: Effect of Curvature in Plain Weave Fabric

Plastic optical fiber was chosen for information delivery media in smart textile. Cladding layer was peeled off by chemical and mechanical methods to find optimal peeling conditions. Both radial side illumination and longitudinal end-tip illumination were measured for visible light of 627 µm wavelength. A half-cone-shaped jig was manufactured using 3D printing to give various curvature conditions to fibers. Also POFs were embedded in plain weave textile structure to measure the light dissipation effect. The waveguide phenomenon was modeled using discrete ray tracing technique and ray-to-interface collision detection algorithm. Results from the proposed modeling technique showed linear relationship with those from experiment.

Underwater fiber–wireless communication with a passive front end

We propose and experimentally demonstrate a novel concept on underwater fiber–wireless (Fi–Wi) communication system with a fully passive wireless front end. A low-cost step-index (SI) plastic optical fiber (POF) together with a passive collimating lens at the front end composes the underwater Fi–Wi architecture. We have achieved a 1.71-Gb/s transmission at a mean BER of 4.97 × 10−3 (1.30 × 10−3 when using power loading) over a 50-m SI-POF and 2-m underwater wireless channel using orthogonal frequency division multiplexing (OFDM). Although the wireless part is very short, it actually plays a crucial role in practical underwater implementation, especially in deep sea. Compared with the wired solution (e.g. using a 52-m POF cable without the UWOC part), the proposed underwater Fi–Wi scheme can save optical wet-mate connectors that are sophisticated, very expensive and difficult to install in deep ocean. By combining high-capacity robust POF with the mobility and ubiquity of underwater wireless optical communication (UWOC), the proposed underwater Fi–Wi technology will find wide application in ocean exploration.

GaN-Based Cyan Light-Emitting Diode with up to 1-GHz Bandwidth for High-Speed Transmission Over SI-POF

We demonstrate the performance of a novel cyan light-emitting diode (LED) on a patterned sapphire substrate for use as a light source for plastic optical fiber (POF) communications with the central wavelength at 500 nm. By significantly reducing the number of active InxGa1-xN/GaN multiple quantum wells and the thickness of the barrier layers down to 5 nm, such a device with an active diameter of 47 μm demonstrates a record high 3-dB electrical-to-optical bandwidth, as high as 1 and 0.7 GHz, among all the reported high-speed visible LEDs under room temperature and 110 °C operation, respectively. TO-Can packaging with a lens is used to enhance the POF coupling efficiency. Very-high data rates of 5.5 and 5.8 Gbit/s are achieved over step index POF under nonreturn-to-zero and 4-pulse amplitude modulation, respectively. When the POF transmission distance reaches 50 m, there is degradation in the maximum data rate for both modulation schemes to 1.3 Gbit/s due to the dispersion and attenuation of the POF.

Achieving 1 Gbps Over Step-Index Plastic Optical Fiber Using Spatial Mode Air-Gap Filter

This letter presents a technique to mitigate the effect of modal dispersion of a standard, 1 mm step-index plastic optical fiber (SI-POF). The modal dispersion is mitigated by reducing the effective numerical aperture of the fiber link. The technique employs a simple spatial mode filter constructed from a polycarbonate capillary tube. We experimentally demonstrated an error-free 1 Gb/s non-return-to-zero transmission over 30 m of SI-POF.

Multi-Rate Adaptive Equalizer for Transmission Over Up to 50-m SI-POF

This letter presents a novel adaptive continuous-time equalizer integrated in a receiver front-end for short-reach high-speed optical communications through low-cost step-index plastic optical fibers (SI-POF). The proposed equalizer is able to compensate the variations in the frequency response and attenuation of a 1-mm diameter SI-POF but it is also able to work at different data rates ranging from 400 Mb/s to 2.5 Gb/s. The prototype has been integrated in a cost-effective standard 0.18- $\mu \text{m}$ CMOS technology, and requires 60 mW of power consumption under just 1-V supply voltage.