We present a unique design of weakly coupled few-mode photonic crystal fiber (FM-PCF), which can support six vector modes (HE11a,HE11b,TM01,HE21a,HE21b, and TE01) with ultra-flattened chromatic dispersion over the C wavelength band. We investigate the impact of fiber parameters on chromatic dispersion, minimum effective refractive index difference (minΔneff), confinement loss, bending loss, and differential mode delay using the finite element method. To achieve ultra-flattened chromatic dispersion and large minΔneff, an extra small elliptical defected hole is introduced in the fiber core. The circular holes in the first ring are replaced by elliptical holes to further obtain flattened-chromatic dispersion. The simulated results show that the designed weakly coupled FM-PCF can obtain an ultra-flattened average dispersion of 0.011 ns/nm/km with a small dispersion slope (<1.5 × 10 − 5 ns / km / nm2) in the wavelength range of 1520 to 1570 nm. And the proposed weakly coupled FM-PCF has large minΔneff (>1 × 10 − 3), low confinement loss (<10 − 4 dB / km), and good bending resistance. In summary, the proposed weakly coupled FM-PCF has potential applications for large-capacity MDM communication systems.
KEYWORDS: Refractive index, Birefringence, Optical engineering, Digital micromirror devices, Tolerancing, Multiplexing, Telecommunications, Cladding, Single mode fibers, L band
We present a weakly coupled bow-tie rectangular dual-step few-mode fiber supporting 20 eigenmodes for short-haul communication systems across the O band. The rectangular dual-step core and bow-tie stress-applying area are introduced to effectively split adjacent eigenmodes. We evaluate the impact of parameters on modal mode effective refractive index difference (MERID) Δneff, min Δneff, min Aeff, Bm, and bending loss at a wavelength of 1310 nm. Broadband performance of the entire O band, including neff, MERID Δneff, differential mode delay, and dispersion, is also analyzed. Results indicate that the 20 eigenmodes supported by the designed fiber are completely separated with MERID Δneff between adjacent modes larger than 2.319 × 10 − 4 over the whole O band. The designed fiber can be used for short-haul multiple-input multiple-output-free eigenmode-division multiplexing systems to improve transmission capacity and expand bandwidth.
Aerosol plays a very important role in the global climate. Due to its short life, changeable sources and sinks and complex physical and chemical and optical properties, it is urgent to grasp the changing trend and its impact on the environment in a large scale through satellite remote sensing technology. This paper expounds the theoretical basis of aerosol detection, introduces the progress of aerosol detection, and puts forward the related technologies of satellite remote sensing to observe atmospheric aerosol.
We propose a 3-dB mode insensitive power splitter (MIPS) capable of broadcasting and combining optical signals. It is fabricated with two identical few-mode fibers (FMFs) by a heating and pulling technique. The mode-dependent power transfer characteristic as a function of pulling length is investigated. For exploiting its application, we experimentally demonstrate both FMF-based transmissive and reflective star couplers consisting of multiple 3-dB mode insensitive power splitters, which perform broadcasting and routing signals in few-mode optical fiber networks such as mode-division multiplexing (MDM) local area networks using star topology. For experimental demonstration, optical on-off keying signals at 10 Gb/s carried on three spatial modes are successfully processed with open and clear eye diagrams. Measured bit error ratio results show reasonable power penalties. It is found that a reflective star coupler in MDM networks can reduce half of the total amount of required fibers comparing to that of a transmissive star coupler. This MIPS is more efficient, more reliable, more flexible, and more cost-effective for future expansion and application in few-mode optical fiber networks.
KEYWORDS: Switching, Optical fibers, Eye, Single mode fibers, Optical switching, Digital signal processing, Signal detection, Receivers, Lithium, Networks
We propose and experimentally demonstrate an all-fiber optical mode switching structure supporting independent switching, exchanging, adding, and dropping functionalities in which each mode can be switched individually. The mode switching structure consists of cascaded mode selective couplers (MSCs) capable of exciting and selecting specific higher order modes in few-mode fibers with high efficiency and one multiport optical switch routing the independent spatial modes to their destinations. The data carried on three different spatial modes can be switched, exchanged, added, and dropped through this all-fiber structure. For this experimental demonstration, optical on-off-keying (OOK) signals at 10-Gb/s carried on three spatial modes are successfully processed with open and clear eye diagrams. The mode switch exhibits power penalties of less than 3.1 dB after through operation, less than 2.7 dB after exchange operation, less than 2.8 dB after switching operation, and less than 1.6 dB after mode adding and dropping operations at the bit-error rate (BER) of 10−3, while all three channels carried on three spatial modes are simultaneously routed. The proposed structure, compatible with current optical switching networks based on single-mode fibers, can potentially be used to expand the switching scalability in advanced and flexible short-reach mode-division multiplexing-based networks.
We proposed a plasmonic-WGM hybrid system composed of a tapered-fiber-coupled microsphere resonator and a PICattached gold tip to focus the incident light into a nanoscale domain (~728.8 nm2) with high coupling efficiency of ~80.3 % and the Q factor of ~1.9×106. In order to experimentally verify the strong interaction between light and matter owing to efficient excitation of localized surface plasmon at the gold-coated tip, we demonstrated to observe two-photon excited fluorescence from PIC dye molecules attached on the gold-coated tip even under a weak CW excitation condition via a tapered-fiber-coupled microsphere resonator.
The efficient coupling of light from a tapered fiber coupled microsphere resonator to localized surface plasmon modes of
Au-coated tip was demonstrated. To verify efficient localized surface plasmon excitation at the metal tip via a tapered
fiber coupled microsphere resonator, we measured second harmonic generation from the top of Au-coated tip. From the
results, in spite of a weak CW excitation, we succeeded in repeatedly observing SHG from the top of the Au-coated tip
via a tapered fiber coupled microsphere resonator system, which could focus the light with the coupling efficiency of
about 63.2 % into the nanoscale domain of the metal tip with the effective cross section of 358.2 nm2.
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