Standard Standard Single-mode Fiber Research Articles

Efficient Mode Conversion from a Standard Single-Mode Fiber to a Subwavelength-Diameter Microfiber

Efficient mode conversion is crucial for hybrid photonic systems. We present efficient light transition from a standard single-mode fiber (SMF) to a subwavelength-diameter microfiber via a relatively short tapered fiber. Numerical simulations were performed to design the tapered morphology with high transmittance (approximately 86%) for the fundamental modes. The designed tapered fiber was successfully fabricated on the top of a cleaved SMF tip by the direct laser writing (DLW) method. For the 1550 nm wavelength, the transmittance from the standard SMF to the subwavelength-diameter microfiber was determined to be 77%, accompanied by a change in the effective mode area from 38 μm2 to 0.47 μm2 within a very short length of 150 μm. Our result demonstrated the versatility of the DLW technique for boosting the mode conversion efficiency of fiber-to-chip devices, enabling various applications in the future.

Novel Inter-Core Crosstalk Measurement Method Using a Loopback and Bidirectional OTDR Technique

Uncoupled multi-core fibers (MCFs) have been reported to increase transmission capacity. One of the issues of MCFs is inter-core crosstalk (XT), which deteriorates communication quality. Measurement of the amount of XT is essential; however, the measurement methods require a measurement system separate from that of standard single-mode fiber (SMF) measurements. In this paper, we propose a novel inter-core XT measurement method using a loopback and bidirectional optical time-domain reflectometer (OTDR) technique. In this measurement, an OTDR is connected to the excitation core at one end of an MCF, and a dummy SMF is connected to the excitation and measured cores at another end. A measured OTDR waveform comprises an excitation core, a dummy SMF, and a measured core. Further, an XT peak appears at the midpoint of the measured OTDR waveform. An XT of homogeneous MCF can be easily calculated from their peak height. The fiber attenuation of excitation and measured cores can be calculated from these waveforms, and the amount of XT and fiber attenuation can be measured simultaneously. Furthermore, in this method, XT can be measured using only OTDR devices, which are the same measurement system as that of the standard SMF. We discussed the measurement mechanism and calculation method of XT amounts and compared the measured XT values with those obtained from the general measurement method using a power meter. We confirmed accurate measurements up to 80 km length of homogeneous MCF; however, the measured error increased when the length was close to the OTDR's noise level.

Splicing of silica-based MOF and standard SMF: Loss evaluation using an enhanced field model

Abstract Splice losses between the transmission optical fibers and the fiber-based devices have been considered as one of the bottlenecks in accomplishing the optical networks. Consequently, the practical utilization of specialty optical fibers such as triangular solid-core microstructured optical fibers (T-MOFs) in conjunction with splicing to dissimilar standard single-mode fiber (SMF) prerequisite a trustworthy, repeatable and robust low-loss splicing. Utilizing an enhanced field model, we appraised the splice losses between two similar T-MOFs without considering collapsing of air-holes at the joint interface with azimuthal and transverse offsets, and the splice loses between T-MOF and classical SMF are also explored. Collapsing of air-holes can facilitate to minimize the mode-profile inconsistency at splicing interface and hence, lowering the losses; therefore, we evaluated the mode-field diameter (MFD) as a function of collapse ratio. We reported splice losses of ~0.378 dB and ~5.032 dB at 1.55 µm between two identical T-MOFs with Λ = 4.0 µm, for the case of azimuthal and transverse offset, respectively. Also, we examined the consistency of our results by evaluating the relative errors, and the comparisons have been incorporated with those as reported in the literature.

Wideband multimode fiber with an optimized core size and fluorine-doped cladding for high-speed SWDM and CWDM transmission.

We propose a novel multimode fiber (MMF) with a 30 μm-core and fluorine-doped cladding for both high-speed short wavelength division multiplexing (SWDM) and coarse wavelength division multiplexing (CWDM) transmission. By optimizing the core size, the mode field diameter (MFD) mismatch between the proposed fiber and both the standard single-mode fiber (SMF) and MMF is minimized, which enables the quasi-single mode operation in the CWDM window and a compromised coupling loss with standard MMFs and SMFs. By adopting a fluorine-doped silica cladding, the bandwidth dependence on wavelength of the proposed fiber is minimized, which indicates that the modal bandwidth performance at the longer wavelength can be effectively improved without compromising modal bandwidth at 850 nm. The error-free 100 Gb/s (4×25.78 Gb/s) multimode transmission over 250 meter-long fiber is achieved using a commercially available VCSEL-based SWDM transceiver. The applicable distance can be extended to 300 meters when a biterror rate just below the forward error correction (FEC) threshold of 5×10-5 is acceptable. Besides, the 100 Gb/s error-free single-mode transmission over 10 km-long fiber was also demonstrated with a commercially available directly modulatedlaser (DML)-based CWDM transceiver. The results imply that the proposed MMF may be useful for large-scale data center applications.

Estimation of Signal-to-Cross Talk Ratio of Stimulated-Raman-Scattering-Induced Cross Talk in Wavelength-Division-Multiplexing-Based Radio-over-Fiber Links

Abstract This paper evaluates the signal-to-cross talk ratio (SXR) of cross talk induced by stimulated Raman scattering (SRS) in radio-over-fiber (RoF) systems based on wavelength-division multiplexing. The reported study has modeled the relations of SXR to modulation frequency, optical power, transmission length, and effective area of fiber for various values of the walk-off parameter. The summary of experimental results reveals that SXR decreases with increases in channel input power and transmission distance and increased with increases in fiber effective area and modulation frequency. Results showed that increasing the walk-off parameter from 13.6 to 81.6 ps/km increased the SXR by almost 6 dBm. Furthermore, various fibers, including standard single-mode fiber (SMF), Corning LEAF, and Alcatel TeraLight were tested for their capacity to mitigate SRS-induced cross talk. These tests demonstrated that standard SMF suppressed SRS cross talk effectively and offered values of SXR 3 dBm and 6 dBm higher than the values exhibited by Alcatel TeraLight and Corning LEAF, respectively.

Orbital Angular Momentum Mode Converter Based on Helical Long Period Fiber Grating Inscribed by Hydrogen–Oxygen Flame

A high-efficiency grating fabrication method was, for the first time, demonstrated to inscribe helical long period fiber gratings (H-LPFGs) in small numbers by means of twisting a standard single-mode fiber (SMF) during hydrogen-oxygen flame heating and then cutting the helical fiber into in series of sections. Each section of the helical fiber was a desired LPFG whose resonant wavelength, i.e., grating pitch, can be changed by adjusting the twist rate of the helical fiber. The H-LPFG inscribed in a standard SMF could be used to generate orbital angular momentum (OAM) modes, i.e., OAM+1 mode, with a purity of 91% and a conversion efficiency of 87% within a large wavelength range from more than the cutoff wavelength of an SMF, which is highly advantageous to all-fiber optical communications based on the OAM mode-division multiplexing technique.

10-/28-Gb Chirp Managed 20-km Links Based on Silicon Photonics Transceivers

High speed directly modulated single mode lasers are becoming important optical components for short reach communication. In order to cover a transmission distance that is required for passive optical network and inter data-center applications, the chirp managed laser is an attractive transmitter technology. This technology enables to use a directly modulated laser for longer reach systems, resulting in a smaller footprint, low fabrication cost, and lower power consumption. Error free 10-Gb/s non-return-to-zero-ON–OFF-keying (NRZ-OOK) data transmission over 20-km standard single mode fiber (SMF) is demonstrated using a heterogeneously integrated III–V-on-Si distributed feedback laser in combination with a tunable optical filter as a transmitter and a Ge-on-Si waveguide-coupled avalanche photodiode with an integrated transimpedance amplifier (TIA) as a receiver. For inter-datacenter applications, by increasing the bias current of the laser (improving its modulation bandwidth and output power) and using a faster silicon-contacted germanium waveguide p-i-n photodetector with an integrated TIA, 28-Gb/s NRZ-OOK data transmission over 20-km standard SMF is demonstrated.

In-line, fiber-optic polarimetric twist/torsion sensor

This letter presents an optical fiber twist/torsion sensor that utilizes dissimilar polarization-preserving characteristics of standard single-mode and high-birefringence fibers. When only one polarization mode of the high-birefringence fiber is excited, spatial orientation of the E-field vector follows the fiber's principal axis orientation, even when the fiber is twisted around its longitudinal axis. This is contrary to a standard single-mode fiber (SMF), where the E-field vector maintains its spatial orientation regardless of the fiber torsional twist. The proposed sensor consists of a short section of standard SMF inserted in between two lead-in polarization-mainlining fibers. Only one mode of the lead-in fiber is excited at the input, while the ratio of both polarization modes is measured at the output side of the fiber assembly in order to determine the torsional twist of a standard SMF. This sensor can be used for measuring unambiguously twist/torsion angles of between ±95°. The sensor demonstrated very low temperature dependence.

Supercontinuum generation from ~19 to 45 μmin ZBLAN fiber with high average power generation beyond 38 μm using a thulium-doped fiber amplifier

A mid-IR supercontinuum (SC) fiber laser based on a thulium-doped fiber amplifier (TDFA) is demonstrated. A continuous spectrum extending from ∼1.9 to 4.5 μm is generated with ∼0.7 W time-average power in wavelengths beyond 3.8 μm. The laser outputs a total average power of up to ∼2.6 W from ∼8.5 m length of ZrF4─BaF2─LaF3─AlF3─NaF (ZBLAN) fiber, with an optical conversion efficiency of ∼9% from the TDFA pump to the mid-IR SC. Optimal efficiency in generating wavelengths beyond 3.8 μm is achieved by reducing the losses in the TDFA stage and optimizing the ZBLAN fiber length. We demonstrate a novel (to our knowledge) approach of generating modulation instability-initiated SC starting from 1.55 μm by splitting the spectral shifting process into two steps. In the first step, amplified approximately nanosecond-long 1.55 μm laser diode pulses with ∼2.5 kW peak power generate a SC extending beyond 2.1 μm in ∼25 m length of standard single-mode fiber (SMF). The ∼2 μm wavelength components at the standard SMF output are amplified in a TDFA and coupled into ZBLAN fiber leading to mid-IR SC generation. Up to ∼270 nm SC long wavelength edge extension and ∼2.5× higher optical conversion efficiency to wavelengths beyond 3.8 μm are achieved by switching an Er:Yb-based power amplifier stage with a TDFA. The laser also demonstrates scalability in the average output power with respect to the pulse repetition rate and the amplifier pump power. Numerical simulations are performed by solving the generalized nonlinear Schrödinger equation, which show the long wavelength edge of the SC to be limited by the loss in ZBLAN.

Fiber-Optic High-Temperature Sensor Based on Thin-Core Fiber Modal Interferometer

We present a new fiber-optic high-temperature sensor based on a thin-core fiber (TCF) modal interferometer. A thin-core fiber, whose core radius is about half of the radius of a standard single-mode fiber (SMF), is inserted between standard SMFs to form an extremely simple in-fiber modal interferometer. The wavelength of the transmission dip increases linearly with the temperature. Experimental demonstration shows that it can be used to sense temperature up to 850 °C with a sensitivity of about 18.3 pm/ °C.

A comparison of single mode and multimode fiber links for use in wireless‐over‐fiber systems

AbstractThis article compares the performance of standard single mode fiber (SMF) with 62.5/125 μm multimode fiber (MMF) for radio‐over‐fiber links using 850 nm multimode vertical cavity surface emitting lasers. The results show SMF links suffer from a coupling loss of 15.3 dB which is compensated by the low loss of SMF compared to MMF in the 2.4–5 GHz radio band. Standard SMF is not single moded at 850 nm and mode filters are employed to obtain a smooth modulation response. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1445–1449, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24362

Application of super-DWDM technologies to terrestrial terabit transmission systems

This paper describes application areas, elemental technologies, and the feasibility of terrestrial terabit wavelength division multiplexing (WDM) transmission systems based on super-dense wavelength division multiplexing (DWDM) technologies with a channel spacing of 12.5 GHz. Numerical simulation results quantitatively show that the merit of super-DWDM transmission is the elimination of the need for dispersion compensation over the several hundreds of kilometers of standard single-mode fiber (SMF). To support super-DWDM transmission, the prototype of a multiwavelength generator, which consists of just an intensity modulator and a phase modulator, is developed as a small-size WDM light source with high-wavelength stability. We use this prototype to conduct a 1.28-Tb/s (512 channels /spl times/ 2.5 Gb/s) transmission experiment with a channel spacing of 12.5 GHz over 320 km (80 km /spl times/ 4 span) of standard SMF without dispersion compensation. The potential and the feasibility of super-DWDM transmission with a channel spacing of 12.5 GHz for terrestrial systems is confirmed by the numerical simulation and the transmission experiment.

Fiber-optic millimeter-wave downlink system using 60 GHz-band external modulation

In this paper, a fiber-optic millimeter-wave (mm-wave) downlink system using 60 GHz-band external modulation is investigated. We prepare the fiber-optic 60 GHz-band mm-wave downlink testbed. It consists of an optical modulation section with a mm-wave signal generator, an optical single sideband (SSB) filter, a standard single-mode fiber (SMF), an optical detection section with a 60 GHz-band radio transmitter and a 60 GHz-band radio receiver. To modulate the laser output with 60 GHz-band mm-wave signals directly, a specially designed electro-absorption modulator with high-efficiency at around 60 GHz is used. The use of this modulator makes the simpler system configuration possible. Using the downlink testbed, the 5 m-long free-space propagation of subcarrier multiplexed 156 Mb/s-DPSK 60 GHz-band mm-wave signals recovered by optical direct detection is successfully demonstrated. The transmission of the mm-wave signals over 85 km-long standard SMF is also successfully demonstrated, using an optical SSB filtering technique to overcome the fiber dispersion. The BER of 10/sup -9/ is achievable at the optical received power of -7.0 dBm.

Unrepeated 40-Gb/s RZ single-channel transmission at 1.55 μm using various fiber types

We investigate experimentally and theoretically the effect of signal power and dispersion compensation scheme in unrepeated return-to-zero single-channel 40-Gb/s 150-km transmission using standard single-mode fiber (SMF), nonzero dispersion shifted fiber [true wave fiber (TWF)] and dispersion shifted fiber (DSF). It is shown, that standard SMF allows significantly higher fiber-input power than nonzero dispersion shifted fiber or dispersion shifted fiber and, therefore, offers larger transmission spans.

10-Gb/s transmission using 1.3-μm low-chirp high-power directly modulated, packaged DFB laser module for short distance (<50 km) applications

We have demonstrated 10-Gb/s transmission over 51 km of standard single-mode fiber (SMF) using a 1.3-μm low chirp high-power directly modulated, packaged DFB laser module. With +7-dBm average laser module power and -16-dBm PIN receiver sensitivity, the power budget is 23 dB, which allows transmission over 50 km of standard SMF without optical amplifiers. In addition, we have investigated the impact of fiber chromatic dispersion on systems performance at 10 Gb/s over a wide range of dispersion. For the dispersion range of -600 to 0 ps/nm, negative power penalties have been observed due to the pulse compression effect which is resulted from a low chirp of the laser. For use of this effect, the distributed-feedback (DFB) laser wavelength needs to be properly selected and its range is found to be as wide as 80 nm for transmission over 50 km of embedded standard SMF cables.

Dispersion-tolerant optical transmission system using duobinary transmitter and binary receiver

We propose a dispersion-tolerant optical duobinary transmission system which uses a binary intensity modulation direct detection (IM-DD) receiver. The proposed system also relaxes the fiber input power limitation due to stimulated Brillouin scattering (SBS). Tolerance to chromatic dispersion in the proposed system is estimated by a simulation. A 10 Gb/s optical duobinary signal can be transmitted over 200 km of standard single-mode fiber (SMF) with 1 dB dispersion penalty. The advantages of the proposed system are confirmed experimentally. The optical duobinary signal was successfully received by the binary IM-DD receiver at the same sensitivity as a binary IM signal. Power penalty due to chromatic dispersion over a 164-km standard SMF was about 1.8 dB at 10 Gb/s. The SBS threshold of the 10 Gb/s optical duobinary modulated light was more than +20 dBm.