Bit-rate Distance Product Research Articles

Single wavelength MDM-PDM 800-Gb/s net data rate transmission over a standard multimode fiber employing a Kramers-Kronig receiver.

We propose a high-speed multimode fiber short-reach optical interconnect system based on a Kramers-Kronig (KK) field reconstruction with the mode division multiplexing (MDM) and polarization division multiplexing (PDM) technology. In this work, the LP01, LP21a, LP21b, and LP02 modes are selected as independent channels to carry information. The demonstration achieved the 800 Gb/s net data rate per wavelength with a bit-rate-distance-product (BDP) of 8 Tb/s·km. To the best of our knowledge, this is the highest experimental record of a single wavelength BDP over the SMMF with KK detection. In addition, we discuss the system performance after all multiple-input multiple-output (MIMO) and partial MIMO processing and give guidance on the trade-off between system performance and computational resource.

Design and Performance Investigation of Intensity Modulation/Direct Detection Scheme for C- and O-band Point-to-Multipoint Optical Networks

The fifth generation (5G) and beyond mobile networks support increasing number of users with increasing bit rate per users. This has encouraged researchers to propose coherent digital subcarrier multiplexing (SCM) point-to-multipoint (P2MP) architectures to reduce the cost and complexity of optical transport networks, particularly in the metro aggregation scenario. However, coherent optical receiver is relatively costly and complexity compared with a direct-detection (DD) counterpart due to the use of a synchronized local laser. This paper addresses design issues and performance investigation of intensity modulation/direct-detection (IM/DD) P2MP optical networks. P2MP architectures are designed using digital RF multisubcarrier (MSC) waveform embedded on the intensity of continuous-wave (CW) laser beside direct-detection scheme. The design covers C- and O-band operation using a wavelength-division multiplexing (WDM) architecture. Further single- and double-polarization (SP and DP) versions are reported for each type of the networks. All the architectures are built in Optisystem version 15 environment and simulated for different network parameters, under the assumption of 25 Gbps per subcarrier data rate. The main performance measures are maximum route reach and bit rate-distance product (BDP). The simulation results indicate that DD networks can replaced the coherent counterpart when number of subcarriers per optical channel is 4. Further, the O-band P2MP networks offer high values of maximum reach and BDP than C-band counterparts.

32 Gb/s physical-layer secure optical communication over 200 km based on temporal dispersion and self-feedback phase encryption.

Providing physical layer security at the lowest network layer in fiber-optic communication systems is a technical challenge worldwide. Here, we propose and experimentally demonstrate a pure hardware optical encryption scheme based on temporal spreading and self-feedback phase encryption for high-speed and long-distance physical-layer secure optical communication. A record high bit-rate-distance product of 6400 Gb/s km is successfully achieved by the secure transmission of a 32 Gb/s on-off-keying modulated confidential signal over a 200 km optical fiber link. The demonstrated scheme is fully compatible with conventional optical transmission systems and can be operated in a pluggable manner, which may pave a new path to ultra-high-speed physical-layer secure optical communication in the future.

PAM4 rolling-shutter demodulation using a pixel-per-symbol labeling neural network for optical camera communications.

The typical optical camera communication (OCC) modulation scheme is based on binary intensity modulation. To increase the transmission data rate, multi-level modulation format is highly desirable. In this work, we bring forward and demonstrate a rolling shutter 4-level pulse amplitude modulation (PAM4) demodulation scheme for OCC systems using pixel-per-symbol labeling neural network (PPSL-NN) for the first time up to the authors' knowledge. A bit-rate distance product of 28.8 kbit/s • m per color is achieved. The proposed scheme is to calculate and re-sample the pixel-per-symbol (PPS) to make sure the same number of pixels in each PAM4 symbol is corresponding to a label for the neural network. Experiment results reveal that the proposed scheme can efficiently demodulate high speed PAM4 signal in the rolling shutter OCC pattern.

Very High Bit-Rate Distance Product Using High-Power Single-Mode 850-nm VCSEL With Discrete Multitone Modulation Formats Through OM4 Multimode Fiber

In order to investigate the tradeoff between optical spectral width and modulation speed of 850-nm Zn-diffusion vertical-cavity surface-emitting laser (VCSEL) and its influence on the performance of discrete multitone (DMT) modulation, two kinds of high-speed VCSEL structures with different cavity lengths (λ/2 and 3λ/2) are studied. By shortening the cavity length to λ/2, allocating the oxide layer in the standing-wave peak, and performing a Zn-diffusion aperture in our VCSEL structure, stable dual mode in the output optical spectra across the full range of bias currents with good high-speed performance (∼16-GHz bandwidth) can be achieved. Compared with its multimode reference, it shows far less roll-off with regard to the maximum data rate versus transmission distance over OM4 multimode fibers under forward error correction (FEC) threshold (BER $ ). On the other hand, for the 3λ/2 VCSEL structure, by using the same Zn-diffusion conditions as those of dual-mode counterpart, highly single-mode operation (side-mode suppression ratio> 35 dB) with high available power can be achieved over the full range of bias currents. Although such device shows a smaller 3-dB electrical-to-optical bandwidth (12 versus 16 GHz) than that of the dual-mode one, it exhibits a superior transmission performance by use of DMT modulation format. A record high bit-rate distance product (107.6 Gb/s·km) at nearly 50-Gb/s transmission under FEC threshold (BER $ ) through 2.2-km OM4 fibers has been successfully demonstrated by the use of single-mode VCSEL with optimized structures. In addition, error-free (BER $ ) transmission at 20.3 Gb/s with bit-rate distance product of 44.66 Gb/s·km has also been demonstrated.

Single-Mode, High-Speed, and High-Power Vertical-Cavity Surface-Emitting Lasers at 850 nm for Short to Medium Reach (2 km) Optical Interconnects

The vertical-cavity surface-emitting lasers (VCSELs) with high single-mode (narrow linewidth) output power are essential to minimize chromatic dispersion and to further improve the bit-rate distance product in a multimode fiber, which has a significant propagation loss (~3.5 dB/km) at 850 nm wavelength. Here, we demonstrate the detailed design considerations and fabrication of a single-mode, high-power, and high-speed VCSELs at the 850 nm wavelength with oxide-relief and Zn-diffusion apertures for the application of short (0.3 km) to medium reach (2 km) optical interconnects. By optimizing the relative geometric sizes between two such apertures in our demonstrated 850-nm VCSELs, we can not only attain high single-mode output power (~6.5 mW), but also with a reasonable threshold current (<; 2.0 mA). Furthermore, the spatial hole burning effect induced low-frequency roll off can also be minimized in our optimized structure to obtain a maximum data rate up to 26 Gbit/s. The record-high bit rate-distance products for OM4 MMF transmission under ON-OFF keying (14 Gbit/s × 2.0 km) modulation formats have been successfully demonstrated by the use of our VCSEL.

Stability of high bit rate quantum key distribution on installed fiber

We present a study of the effects of ambient fluctuations on the bit rate stability of a quantum key distribution (QKD) link operating on installed fiber. Secure quantum keys were distributed continuously for 60 hours over 45km of installed fiber. A total of 6.33 × 1010 bits were exchanged during this period, the largest volume of secure keys distributed on installed fiber in a single continuous session to date. We report a record bit-rate distance product for QKD of 13.2 × 106 (bits/s)-km.

WDM Transmission of 16&amp;lt;tex&amp;gt;$,times,$&amp;lt;/tex&amp;gt;10.709 Gb/s Over 640-km SSMF Using Cascaded Semiconductor Optical Amplifiers and DPSK Modulation Format

To extend transmission distance using cascaded in-line semiconductor optical amplifiers (SOAs) and differential phase-shift-keying modulation format, optimal operation conditions for SOAs, such as input power and operation current, are studied. 16/spl times/10.709-Gb/s wavelength-division-multiplexing transmission over 640-km SSMF with the optimal system design parameters is demonstrated. This is, to the best of our knowledge, the largest bit-rate distance product reported.

2.5 Gbit/s transmission of spectrum-sliced fibre amplifier light source channels over 200 km of dispersion-shifted fibre

Transmission of 2.5 Gbit/s spectrum-sliced fibre amplifier light source channels over 200 km of dispersion-shifted fibre (DSF) has been achieved, the highest bit-rate distance product 500 Gbit/skm using incoherent light sources reported to our knowledge. The total power penalty was as low as 0.2 dB for the 1.8 nm bandwidth channel centred at the zero-dispersion wavelength of DSF.

1.7 Gbit/s transmission over 165 km of dispersion-shifted fibre using spectrum-sliced fibre amplifier light source

The authors have demonstrated 1.7 Gbit/s transmission over 165 km of dispersion-shifted fibre using a spectrum-sliced fibre amplifier light source. To the authors' knowledge, this represents the largest bit-rate distance product (280 Gbit/s km) ever demonstrated using an incoherent light source. The dispersion penalty was very small ( approximately 0.3 dB) even at a wavelength 10 nm away from the dispersion-zero wavelength of the fibre.

Long distance transmission through distributed erbium-doped fibers

High bit rate, all-optical long-distance transmission could be created through the combined use of loss-compensating gain in erbium-doped fibers and solitons. A detailed analysis of the distributed erbium-doped fiber, including the spectral-gain dependency, is combined with an optimum design of the transmission fiber and general bit-error-rate calculations. Changes in wavenumber, group velocity, and fiber dispersion due to erbium doping in a single-mode fiber are evaluated, and a reduction in bit-error rates due to the erbium spectral-gain profile is shown. Transmission through distributed erbium-doped fiber with 100-km separation between each pump-power station is shown, with a total bit-rate distance product of 55 Gb/s . Mm.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Limits of long-distance soliton transmission in optical fibers with laser diodes as pulse sources

To employ soliton transmission in practical optical fiber communication systems, it is desired that semiconductor laser diodes (LDs) can be used as the optical soliton sources. The authors show that, when pulses generated by LDs are used for soliton transmission, the large frequency noise of LDs causes jitter in soliton arrival times, and makes a limit on the bit-rate distance product of the soliton transmission system. This limit is shown to be proportional to the square root of the output peak power of the pulses generated by LDs, and has a value of 12800 GHz-km for pulses with an output peak power of 10 mW and a duration of 20 ps. >

Attenuation and bit-rate limitations in LED/single-mode fiber transmission systems

In this analysis, distortion of the spectral distribution of the light due to the wavelength dependence of the loss in the fiber is taken into account. The computations show that the system performance of a given fiber type may be characterized by three parameters, one for attenuation and two for dispersion. The attenuation in the fiber may be modeled by an average attenuation per unit length, whereas the bit rate that limits the sensitivity degradation in the receiver due to intersymbol interference to less than 1 dB may be modeled by a bit-rate distance product and a constant bit rate valid for long lengths of fiber. As a design aid in system planning, diagrams showing the three parameters as functions of the diode center wavelength and the spectral width for typical single-mode fibers have been prepared. >

Foreword to the special issue of the Journal of Lightwave Technology on high-speed technology for lightwave applications

HE 1980’s may well be noted in lightwave history for a seemingly endless stream of record breaking improvements in high-speed technology for devices and systems. At the start of the decade, first generation commer. cia1 digital lightwave systems typically operated at data rates below 100 Mbit/s. In laboratory experiments, rates from a few hundred megabits per second to 1 Gbit/s were being explored, with some special devices reaching speeds of a few gigahertz. Advances since then in several technologies have led to phenomenal increases in device and system speeds. The surpassing of the 1-Gbit/s data rate in laboratory transmission experiments led quickly to “hero” experiments at 2, then 4, and now 8 Gbit/s. These experimental systems transmitted data over substantial fiber spans, typically in the 50-200 km range. Laboratory system performance, as measured by the bit-rate distance product, increased from little more than 10 Gbit/s - km in 1980 to nearly 1000 Gbit/s km by the end of 1986. Commercial lightwave systems now span close to 50 km at 1.7 Gbit/s, and higher system bit rates and span lengths are in the planning stage. This Special Issue on High Speed Technology for Lightwave Applications is intended both to document the recent progress made in high-speed device and system performance, and to expose new techniques which may help to extend the current performance limits in the future. The special issue contains 24 papers, of which seven are invited and 17 have been contributed. These papers cover a broad range of topics in high-speed lightwave technoiogy, where high speed is defined for this purpose as operation at bit rates beyond 1 Gbit/s. The papers are presented in four groups: receivers, transmitters, modulators and electronics, and systems. Nearly all aspects of highspeed technology are covered. It is heartening to note the extension of optoelectronic integrated circuitry and coherent optical transmission techniques to multi-gigabitper-second rates, for this will ensure much exciting research and development in those fields in the decade ahead. We hope this special issue stimulates more generally new areas of interest in high-speed technology for lightwave applications. The guest editors thank all of those who contributed to make this special issue possible-our many contributors and reviewers. Special thanks go to our secretarial staffs, who worked tirelessly to manage the enormous flow of paperwork required by this international project.

Dispersion penalty analysis for LED/single-mode fiber transmission systems

GREAT DEAL of attention has been focused recently on telecommunication systems based on single-mode fiber (SMF) and LED light sources for future deployment in the local network and subscriber loop. These systems combine the advantages of the low loss, large bandwidth, and upgrade potential of single-mode fiber with the high reliability and temperature stability, as well as the low cost of LED’s. Recent experiments have demonstrated the feasibility of LED-SMF ’ systems for transmission rates up to 560 Mbit/s and span lengths (at 140 Mbit/s) up to 50 km [1]-[lo]. Chromatic dispersion is a potential limitation at these bit rates and span lepgths, however, because of the broad spectral widths of LED’s. Even for a practical system of shorter transmission distance, the dispersion penalty remains an important consideration in the power budget since the total power coupled into single-mode fiber is relatively small for LED systems. It is thus important to have realistic estimates of dispersion penalties in LED-SMF system design. Penalties for chromatic dispersion in multimode fiber have been calculated for LED’s based on the assumptions of an optical receiver which has been re-equalized to compensate for the fiber dispersion, and an f receiver noise spectral density [ 111, [12]. In practical systems, however, these assumptions are often not applicable. In this paper we present a new calculation of dispersion penalties arising from intersymbol interference for LED-SMF systems with no re-equalization (the more commonly adopted scheme), and compare the results obtained with a treatment of the re-equalized system which considers both white, andf2 receiver noise spectral densities. Simple approximations of dispersion penalties are derived, and bitrate distance product limits are presented as a useful estimation tool for system feasibility studies. Single-mode fiber transmission experiments at 90, 140, and 560 Mbit/ s have been performed using 1.3- and 1.5-pm LED’s [3][6], and the measured dispersion penalties are compared with the results of the above analysis.