The growing bandwidth demands of advanced driver assistance systems (ADAS) and infotainment technologies make Gigabit Ethernet over plastic optical fiber (POF) a natural choice for next-generation automotive data networks, especially in light of the recent approval of the IEEE 802.3bv standard for Gigabit Ethernet transmission over POF. POF-based transmission provides the advantages of low cost, light weight, easy termination, durability, and immunity to electromagnetic interference (EMI), while Gigabit Ethernet extends the current maximum data rate of 150 Mb/s provided by Media Oriented Systems Transport (MOST). Thus, we examine important design choices that impact the performance of POF-based automotive data links for data rates up to and beyond 1 Gb/s and different choices of modulation format, including NRZ and PAM-n. Because simulation is an efficient and cost-effective solution for studying the complex interplay of multiple design choices without requiring physical prototypes, we base our analysis on a comprehensive modeling framework for optical communication systems incorporating large-core step-index fiber and fiber-to-fiber connectors. We study anticipated system performance in terms of bandwidth and BER for different choices of link length and connector count, including the IEEE 802.3bv targets of 15 meters with four connectors and 40 meters with no connectors. In addition, we consider the impact of connector misalignments (both lateral and longitudinal) and source launch profile (measured in terms of its encircled angular flux, or EAF), which also directly affect link bandwidth.
We propose a method for developing small all-fiber vehicle laser rangefinders that is based on pulse position modulation (PPM) and data integration and present a theoretical study on its performance. Compared with spatial coupling, which is employed by most of the current commercial vehicle laser rangefinders, fiber coupling has the advantage that it can guide laser echoes into the interior of a car, so the electronic components following the photodiode can operate in a moderate-temperature environment. However, optical fibers have numerical apertures (NAs), which means that a laser beam from a receiving lens cannot be coupled into an optical fiber if its incident angle exceeds the critical value. Therefore, the effective size of the receiving lens is typically small since it is limited by its focal length and the NA of the fiber, causing the power of the laser echoes gathered by the receiving lens to be insufficient for performing target identification. Instead of increasing the peak transmitting laser power unrestrictedly, PPM and data integration effectively compensate for the low signal-to-noise ratio that results from the effective receiving lens size reduction. We validated the proposed method by conducting numerical simulations and performance analysis. Finally, we compared the proposed method with pseudorandom noise (PN) code modulation and found that, although the two methods perform equally well in single-target measurement scenarios, PPM is more effective than PN code modulation for multitarget measurement. In addition, PPM enables the transmission of laser beams with higher peak powers and requires less computation than PN code modulation does.
A stable reproducible optical standard source for measuring multimode optical fiber attenuation is required as recent
round robin measurements of such fibers at several international companies and national standards organizations showed
significant variation when using a source having only the encircled flux in the near field emerging from it defined. The
paper presents and compares the far field modal power distributions for (i) 2 km and 3 km step-index multimode Hard
Plastic Cladding Fibers, HPCF, (SI-MMF) with 200 μm silica core diameter, 0.37 numerical aperture (NA) and polymer
cladding, (ii) a 10 m silica graded-index multimode fiber (GI-MMF) with 50 μm core diameter and 0.2 NA, and (ii) a
near field Encircled Flux Mode Convertor or “modcon”. A free space method for measuring the far field using a Lightemitting
diode (LED) centered at 850 nm wavelength with 40 nm 10 dB-bandwidth and a charge-coupled device (CCD)
camera is compared with a f-theta multi-element lens based far field pattern (FFP) system. Mandrels of different
diameter and different numbers of turns of the fiber around them were used to achieve an equilibrium mode distribution
(EMD) for the GI-MMF. The paper defines encircled angular flux (EAF) as the fraction of the total optical power
radiating from a multimode optical fiber core within a certain solid angle in the far field. The paper calculates the EAF
when the solid angle increases from the far field centroid.
We have developed a LIDAR system with a sensor head which, although it includes a scanning mechanism, is less than
20 cc in size. The system is not only small, but is also highly sensitive.
Our LIDAR system is based on time-of-flight measurements, and incorporates an optical fiber. The main feature of our
system is the utilization of optical amplifiers for both the transmitter and the receiver, and the optical amplifiers enable
us to exceed the detection limit set by thermal noise. In conventional LIDAR systems the detection limit is determined
by the thermal noise, because the avalanche photo-diodes (APD) and trans-impedance amplifiers (TIA) that they use
detect the received signals directly. In the case of our LIDAR system, the received signal is amplified by an optical fiber
amplifier before reaching the photo diode and the TIA. Therefore, our LIDAR system boosts the signal level before the
weak incoming signal is depleted by thermal noise. There are conditions under which the noise figure for the
combination of an optical fiber amplifier and a photo diode is superior to the noise figure for an avalanche photo diode.
We optimized the gains of the optical fiber amplifier and the TIA in our LIDAR system such that it would be capable of
detecting a single photon. As a result, the detection limit of our system is determined by shot noise.
We have previously demonstrated scanning up to a range of 80 m with this LIDAR system with a 2 mm diameter of
receiving lens. We improved the optical amplifier and the peak output power of LIDAR was over 10KW. We redesigned
the sensor-head and improved coupling efficiency. As a result, we succeeded in scanning over a range of 100 m.
This small and highly sensitive measurement technology shows great potential for use in LIDAR.
We have developed a LIDAR system with a sensor head which, although it includes a scanning mechanism, is less than
20 cc in size. The system is not only small, but is also highly sensitive.
Our LIDAR system is based on time-of-flight measurements, and incorporates an optical fiber. The main feature of our
system is the utilization of optical amplifiers for both the transmitter and the receiver, and the optical amplifiers enable
us to exceed the detection limit set by thermal noise. In conventional LIDAR systems the detection limit is determined
by the thermal noise, because the avalanche photo-diodes (APD) and trans-impedance amplifiers (TIA) that they use
detect the received signals directly. In the case of our LIDAR system, the received signal is amplified by an optical fiber
amplifier before reaching the photo diode and the TIA. Therefore, our LIDAR system boosts the signal level before the
weak incoming signal is depleted by thermal noise. There are conditions under which the noise figure for the
combination of an optical fiber amplifier and a photo diode is superior to the noise figure for an avalanche photo diode.
We optimized the gains of the optical fiber amplifier and the TIA in our LIDAR system such that it would be capable of
detecting a single photon. As a result, the detection limit of our system is determined by shot noise.
We have previously demonstrated optical pre-amplified LIDAR with a perfect co-axial optical system[1]. For this we
used a variable optical attenuator to remove internal reflection from the transmission and receiving lenses. However, the
optical attenuator had an insertion loss of 6dB which reduced the sensitivity of the LIDAR. We re-designed the optical
system such that it was semi-co-axial and removed the variable optical attenuator. As a result, we succeeded in scanning
up to a range of 80 m.
This small and highly sensitive measurement technology shows great potential for use in LIDAR.
Photopolymer based three-dimensional (3D) waveguide devices are very attractive in low-cost optical system
integration. Especially, Light-Induced Self-Written (LISW) technology is suitable for this application, and the
technology enables low-loss 3D optical circuitry formation from an optical fiber tip which soaked in photopolymer
solution by employing its photo-polymerization due to own irradiation from the fiber tip. This technology is expected
drastic mounting cost reduction in fields of micro-optic and hybrid integration devices assembly. The principle of the
LISW optical waveguides is self-trapping effect of the irradiation flux into the self-organized waveguide, where, used
wavelength can be chosen to fit photopolymer's reactivity from visible to infrared. Furthermore, this effect also makes
possible grating formation and "optical solder" interconnection. Actually fabricated self-written grating shows well
defined deep periodic index contrast and excellent optical property for the wavelength selectivity. And the "optical
solder" interconnection realizes a passive optical interconnection between two faceted fibers or devices by the LISW
waveguide even if there is a certain amount of gap and a small degree of misalignment exist. The LISW waveguides
grow towards each other from both sides to a central point where the opposing beams overlap and are then combined into
one waveguide. This distinctive effect is confirmed in all kind optical fibers, such as from a singlemode to 1-mm-corediameter
multimode optical fiber. For example of complicated WDM optical transceiver module, mounted a branchedwaveguide
and filter elements, effectiveness of LISW technology is outstanding. In assembling and packaging process,
neither dicing nor polishing is needed. In this paper, we introduce LISW technology principles and potential application
to integrated WDM optical transceiver devices for both of singlemode and multimode system developed in our research
group.
We developed a LIDAR system with a sensor head as small as 22 cc, in spite of the inclusion of a scanning mechanism.
This LIDAR system not only has a small body, but is also highly sensitive.
Our LIDAR system is based on time-of-flight measurements, and it incorporates an optical fiber. The main feature of our
system is the utilization of optical amplifiers for both the transmitter and the receiver, and the optical amplifiers enabled
us to exceed the detection limit of thermal noise. In conventional LIDAR systems the detection limit is determined by
thermal noise, because the avalanche photo-diodes (APD) and trans-impedance amplifiers (TIA) that they use detect the
received signals directly. In the case of our LIDAR system, received signal is amplified by an optical fiber amplifier in
front of the photo diode and the TIA. Therefore, our LIDAR system can boost the signal level before the weak incoming
signal is depleted by thermal noise. There are conditions under which the noise figure for the combination of an optical
fiber amplifier and a photo diode is superior to the noise figure for an avalanche photo diode.
We optimized the gain of the optical fiber amplifier and TIA in our LIDAR system such that it is capable of detecting a
single photon. As a result, the detection limit of our LIDAR system is determined by shot noise.
This small and highly sensitive measurement technology shows great potential for use in LIDAR with an optical
preamplifier.
Pseudo Random Noise (PN) coded laser radar can improve the target detection ability without the demand on high power
laser. However, the reflected echoes are generally so weak that they are buried in the thermal noise of the receiver, which
raises the problem of choosing an optimal threshold for correctly decoding them since the power of echoes varies from
time to time, and the voltage of light generated electrical signal by photo diode (PD) is always positive. In this work, we
firstly show the problem we are going to discuss. Then, a novel method basing on Inter Symbol Interference (ISI) is
proposed for solving the problem. Next, numerical simulations and experiments are performed to validate the method.
Finally, we discuss the obtained results theoretically.
Polymer optical chip containing a combination of 45°-angled cut waveguide, Y-splitter and S-bend structures was
designed and fabricated for simple and reliable evaluation of multi-mode waveguides. Effect of mode scramblers was
investigated as an appropriate input condition for standardization of measurement of optical characteristics of multi-mode
waveguides.
We developed a novel waveguide fabrication technology, i.e., femtosecond (fs) pulse laser assisted self-writing
waveguide technology, to overcome problems of standard technologies, such as time consuming and high cost. Based on
a light induced self-written (LISW) waveguide fabrication technology, a 488nm cw laser was launched through an
optical fiber into UV curable resin. At the same time a 800nm fs laser was additionally used as a 3D position selective
assistant beam. As the UV resin was cured by the 488nm laser and 800nm fs laser irradiation, a fiber/waveguide
connecting 2D/3D waveguide was easily fabricated.
Plastic optical fibers (POFs) are beginning to replace electrical wiring in many automotive and home applications. In view of this, we have reported the inexpensive wavelength-division-multiplexing (WDM) device for POF system using the LISW waveguide. The LISW waveguides are an attractive and a low-cost process for realizing self alignment between a POF and a waveguide. In this study, we have investigated about the method for precisely aligned LISW polymeric optical waveguides by using an "optical solder" effect. The "optical solder" effect makes it possible to realize a waveguide connection between two faced optical fibers by radiating from both sides even if a significant gap and a small degree of misalignment exist. When we utilize POFs with core diameters of 700μm, waveguides are combinable on the condition that an offset is 700μm or less and a gap is from 6mm to 13mm. By applying this effect, we fabricated precisely positioned LISW waveguides for optical devices. The fiber ends were set at certain mounting positions with respect to the LEDs and PDs. And we evaluated the positioning accuracy. The resulting positional accuracy at the extremities of the optical waveguides is less than one-tenth of the optical fiber core diameter. This value is sufficiently accurate to realize passive alignment. And this result creates new possibilities for boosting the yield of optical modules in mass-production.
A new fabrication technique is proposed for the fabrication of optical waveguides for use in optical communication modules with large-core optical fibers. The proposed technique employs a mixed photopolymerizable resin containing two kinds of photopolymerizable monomers that are different in terms of both refractive index and spectral sensitivity. Visible light is irradiated into the resin through an optical fiber in order by take advantage of the self-trapping effect to form the core portion. Only the lowest refractive index monomer is polymerized, with the reaction proceeding from the end of the fiber tip. After the irradiation is over, a concentration gradient is induced in the low refractive index monomer due to the selective area polymerization, which brings about a counter-diffusion phenomenon of the monomeric materials. Diffusion of the low refractive index monomer causes the high refractive index monomer to move out into the region surrounding the core portion. All of the residual monomers are subsequently cured by exposure to UV light. The region with decreased concentration of high refractive index monomer forms a cladding layer. The resultant refractive index profiles of the waveguides were experimentally observed to be "W-shaped". The measured propagation loss of a 700-μm-diameter waveguide was 1.7dB/cm at 0.68-μm wavelength. We are convinced that this technology could serve to automate optical fiber connection and packaging processes in the assembly of optical waveguide modules. This technology is especially useful in short-haul optical communication systems requiring a large-core optical fiber.
We developed the bidirectional optical transceiver module that combined the two LED light sources of different wavelength and three-dimensional (3-D) optical waveguides. By using a light-induced self-written (LISW) technique, we fabricated and tested 3-D optical waveguide circuits for a plastic optical fiber (POF) WDM full-duplex communication module. Because of the large diameter of the POF, an optical waveguide has the advantages, as compared to conventional lens based modules, of a small size and optical low-loss features. The LISW waveguide enables optical components to connect automatically even if the circuit in the module is complex. In this paper, we demonstrate newly developed bidirectional WDM optical module containing 3-D optical circuits, i.e. a branching waveguide and a reflection waveguide, and their optical properties. The module using commercially available green and red LED was constructed and the two-way communication on IEEE1394-S100 (125Mbps) protocol was verified through 10m-length of POF.
Data links incorporating a green light source at 520nm are required for use with polymethyl methacrylate (PMMA) plastic optical fiber (POF) systems because they have a lower attenuation coefficient compared with conventional red light sources at 650nm. Recently, green LEDs have been developed based on Gallium Nitride (GaN) materials, and high optical output power GaN green LED lamps are now commercially available for general use in display applications. In this paper, we describe in detail the fundamental characteristics of these GaN green LEDs that are due to be employed in POF data links. We evaluate the temperature coefficients of the optical output power and the center wavelength shift and also demonstrate a green LED POF data link that complies with IEEE 1394 S100 operation. GaN green LEDs seem to be promising candidates as light sources for the next generation of POF data links for automotive applications or for long distance In-house multimedia networks. This is because, as we will show, they can operate both at high temperatures and with reduced temperature sensitivity compared with red LEDs fabricated from AlGaInP materials.
In order to simultaneously realize high-speed data transmission, low-cost and lightweight network in automotive applications, a 3(lambda) WDM has been considered to be a suitable solution. We have developed two types of low-cost WDM modules using a polymer optical circuit. As the first method, we developed a planar optical circuit for interconnection between an optical fiber and an LD/PD chip using a PMMA waveguide having out-of-plane branching mirrors, fabricated simultaneously with a waveguide from a polymer film, using a newly-developed temperature-controlled RIE (Reactive Ion Etching) technique. The waveguide has a large diameter (100 x 100micrometers ) and a high-(Delta) (NA=0.5) structure. Transmission losses were 0.1 dB/cm (660nm), and 0.3 dB/cm (1320nm). As the second method, we employed a light-induced waveguide technology for the WDM module fabrication. When a GI optical fiber is soaked in two kinds of light-hardening resin blends in which the hardening wavelength differs ((lambda) 1>(lambda) 2) , the resin is irradiated with (lambda) 1 light through the fiber, a hardened polymer waveguide having uniform diameter geometry would grow from the fiber tip. This method does not need any fiber alignment and packaging process; therefore, cost-effective module fabrication can be expected. This technique utilizes the self-focusing phenomenon of the optical fiber's outgoing beam by a refractive index increase in the material hardening process. We could also confirm two key component formations necessary for the WDM module: regrowth of the waveguide form the backside of a WDM filter after passing through it, and a 90 degree(s) reflected waveguide using a 45 degree(s) mirror.
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