Error-free Transmission Distance Research Articles

Precise measurements and their analysis of GAWBS-induced depolarization noise in various optical fibers for digital coherent transmission.

We undertake precise measurements of guided acoustic wave Brillouin scattering (GAWBS) depolarization noise caused by the TR2,m mode (torsional and radial mode) in various fibers and analyze the results. And we describe the influence of the noise on digital coherent transmission. We first show that the TR2,m mode is distributed over a wider bandwidth when the effective core area Aeff of the fiber is smaller. We then describe the strong mode-number dependence of the depolarization power generated from the profile of the refractive index change induced by the TR2,m mode. We also use two methods to measure the polarization crosstalk (XT) induced by the depolarization, namely, a direct detection method with a photodiode and a conventional power detection method with an optical spectrum analyzer. The results of the two methods agree well, and the XT increase is inversely proportional to the fiber Aeff and proportional to fiber length. Finally, we evaluate the influence of the GAWBS-induced XT on the BER characteristics in a coherent QAM transmission, where we find that the influence of the TR2,m mode is much weaker than that of the R0,m mode (radial mode). That is, the error-free transmission distance in standard single-mode fiber is extended to 8600 km for 256 QAM signal assuming hard-decision FEC with a 7% overhead. This distance is seven times longer than that obtained with the R0,m mode.

Theoretical and experimental analyses of GAWBS phase noise in various optical fibers for digital coherent transmission.

We describe the fiber structural dependence of guided acoustic-wave Brillouin scattering (GAWBS) phase noise in a digital coherent optical fiber transmission. We present theoretical and experimental analyses of GAWBS phase noise spectra in three types of optical fibers and show that the GAWBS resonant modes are distributed over a wider bandwidth as the effective core area of the fiber becomes smaller. We also use a vector signal analysis to show phase fluctuations caused by GAWBS. On the basis of these analyses, we show that the GAWBS phase noise fluctuation has a Gaussian distribution, which is used to evaluate its influence on the BER characteristics in a coherent QAM transmission. As a result, we found that the error-free transmission distance in SSMF is limited to 4600, 1200, and 340 km with 64, 256, and 1024 QAM, respectively, assuming a hard-decision FEC with a 7% overhead. These results provide useful insights into the influence of GAWBS on digital coherent transmission.

Optical wireless APD receivers in 035 µm HV CMOS technology with large detection area

The development of two high-speed monolithically integrated optical receivers for wireless optical communication is presented from the design phase to the measurement. The first high-speed receiver is the modified previous design with an integrated 200-µm diameter avalanche photodiode. The redesign improved the optical sensitivity by 3.7 dB resulting in the sensitivity of -35.5 dBm at 1 Gbit/s. The second receiver is an avalanche photodiode receiver with increased photodiode diameter of 400 µm with a sensitivity of -34.7 dBm at 1 Gbit/s. The receivers were employed in wireless optical communication experiments under various ambient light conditions. The maximum error free transmission distance is 22 m at 1 Gbit/s OWC link. The limits of the used standard 0.35 µm HV CMOS technology are estimated in terms of maximum possible detection area of avalanche photodiode receiver still capable for Gbit data rates.

Multichannel Ultrasonic Data Communications in Air Using Range-Dependent Modulation Schemes.

There are several well-developed technologies of wireless communication such as radio frequency (RF) and infrared (IR), but ultrasonic methods can be a good alternative in some situations. A multichannel airborne ultrasonic data communication system is described in this paper. ON-OFF keying (OOK) and binary phase-shift keying (BPSK) modulation schemes were implemented successfully in the system by using a pair of commercially available capacitive ultrasonic transducers in a relatively low multipath indoor laboratory environment. Six channels were used from 50 to 110 kHz with a channel spacing of 12 kHz, allowing multiple 8-bit data packets to be transmitted simultaneously. The system data transfer rate achieved was up to 60 kb/s and ultrasonic wireless synchronization was implemented instead of using a hard-wired link. A model developed in the work could accurately predict ultrasonic signals through the air channels. Signal root mean square (rms) values and system bit error rates (BERs) were analyzed over different distances. Error-free decoding was achieved over ranges up to 5 m using a multichannel OOK modulation scheme. To obtain the highest data transfer rate and the longest error-free transmission distance, a range-dependent multichannel scheme with variable data rates, channel frequencies, and different modulation schemes, was also studied in the work. Within 2 m, error-free transmission was achieved using a five-channel OOK with a data rate of 63 kb/s. Between 2 and 5 m, six-channel OOK with 60 kb/s data transfer rate was error free. Beyond 5 m, the error-free transmission range could be extended up to 10 m using three-channel BPSK with a reduced data rate of 30 kb/s. The situation when two transducers were misaligned using three-channel OOK and BPSK schemes was also investigated in the work. It was concluded that error-free transmission could still be achieved with a lateral displacement of less than 7% and oblique angles of less than 7°, and three-channel BPSK proved to be more robust than three-channel OOK with transducer misalignment.

Long-distance Transmission of the Multi-channel High-speed Space Camera Data

In order to solve the problem of the short transmission distance and the high bit-error ratio of multichannel high-speed space camera, an active equalization scheme at the receiver end is proposed and implemented. First of all, the non-dc-balanced characteristics of image data signal is analyzed. Based on the measurement data, the mathematical model of the long transmission cable is created. According to the attenuation characteristics of this model, an equalization circuit is designed, which makes use of the high gain of the high-speed differential amplifier and the frequency selecting feature of the phase-lead feedback network to flatten the frequency response of the lossy transmission channel. The simulation results show that with the equalization circuit the maximum data transfer rate of the channel can be expended from 16 Mbps to 250 Mbps. Besides, the eye diagram measurement results demonstrate that the inter-symbol interference caused by the transmission media is significantly reduced after equalization, resulting in an open eye diagram with reduced jitter and crisp edges. Finally, by observing the Signal Tap logic analyzer, sending grayscale and actual pictures, it has been verified that the error-free transmission distance can reach 80 m at 250 Mbps.

Reduction of nonlinear intrachannel effects by channel asymmetry in transmission lines with strong bit overlapping

We have examined the statistics of simulated bit-error rates in optical transmission systems with strong patterning effects and have found strong correlation between the probability of marks in a pseudorandom pattern and the error-free transmission distance. We discuss how a reduced density of marks can be achieved by preencoding optical data.

Nonlinear and noise limitations in dispersion-managed soliton wavelength-division multiplexing transmissions with distributed Raman amplification

We the study limitations to error-free transmission distance as set by noise accumulation and nonlinear pulse interactions in dispersion-managed Nx40-Gbit/s transmission systems with either distributed backward Raman amplification or lumped erbium-doped fiber amplifiers. Significant performance improvement is achievable with Raman amplification.

System application of 1.5 [micro sign]m ultrafast saturable absorber in 10 Gbit/s long-haul transmission

A semiconductor saturable absorber based on a heavy-ion-irradiated quantum well vertical cavity is implemented in a 10 Gbit/s RZ loop transmission. Induced reduction of amplified spontaneous emission accumulation is experimentally demonstrated for the first time to improve the error-free transmission distance by a factor of 2.5.

Recirculating loop demonstration of 40 Gbit/s all-optical 3R data regeneration using a semiconductor nonlinear interferometer

Cascaded 40 Gbit/s 3R data regeneration is demonstrated for the first time, using an all-optical semiconductor nonlinear interferometer. With a regenerator spacing of 100 km, the error-free transmission distance in a recirculating loop is extended by an order of magnitude, from 200 km to greater than 2000 km, thus demonstrating the excellent cascadablility of such a device.