On the multipath interference mitigation for high-speed IM-DD transmissions with Nyquist subcarrier modulation.

The performance of high-speed intensity modulation direct detection (IM-DD) transmissions is severely degraded due to the occurrence of multipath interference (MPI), especially when a higher-order modulation format is utilized. Here, we propose and demonstrate, for the first time to the best of our knowledge, that a Nyquist subcarrier modulation (Nyquist-SCM) format inherently exhibits resistance to the MPI. We experimentally evaluate the MPI tolerance by transmitting 56 Gbit/s PAM-4 signals and Nyquist-SCM 16QAM signals over the 2 km standard single-mode fiber (SSMF) when the C-band semiconductor laser with a linewidth of 1.7 MHz is utilized. In comparison with the PAM-4 format, the Nyquist-SCM 16QAM format can lead to an enhanced MPI tolerance of 4 dB at the KP4-FEC threshold of BER = 2 × 10-4. In addition, even with the help of MPI mitigation for the PAM-4 signals based on two newly reported methods, the utilization of Nyquist-SCM 16QAM signal can still guarantee an improved MPI tolerance of 1 dB.

Pairwise Tomlinson-Harashima precoding for multiple-lane IM-DD transmissions.

As for the photonic interconnection based on the multiple-lane intensity modulation direct detection (IM-DD) transmission, both intra-channel inter-symbol-interference (ISI) originating from bandwidth constraint, and inter-channel performance discrepancy emerging from inter-channel component differences are the major bottleneck for the throughput enhancement. Here, we propose a pairwise Tomlinson-Harshima precoding (P-THP) scheme, in order to simultaneously deal with both intra-channel ISI and inter-channel performance discrepancy. The effective function of the proposed P-THP scheme is experimentally evaluated by transmitting 4-channel 81-GBaud PAM4 signals over 2 km standard single-mode fiber (SSMF). Compared with the conventional scheme with only applying THP on individual wavelength channel, the required optical received power (ROP) under the back-to-back (B2B) transmission can be reduced by 0.75∼1 dB with the help of proposed P-THP in different experimental component configurations, at the 7% hard decision forward error correction (HD-FEC) threshold of BER = 3.8 × 10-3. After the 2 km SSMF transmission, only the use of proposed P-THP can guarantee to reach the designated HD-FEC threshold, leading to a net rate of >600 Gbit/s.

Solid-state pulse forming module with adjustable pulse duration.

A new solid-state pulse forming module is described in this paper. The pulse forming module is fabricated on a glass ceramic substrate, with the dimension of 250 mm × 95 mm × 4 mm. By changing the copper strips used in the pulse forming modules, the pulse duration of the obtained pulsed can range from 80 ns to 140 ns. Both the simulation and tests show that the pulse forming module has a good pulse forming ability. Under a high voltage in microsecond's time, the new pulse forming modules can hold off a voltage up to 25 kV higher than that of the previous study. In addition, future optimization for the field enhancement near the thin electrode edge has been proposed and simulated.

Reconstruction of complex soft-tissue defects in the extremities with chimeric anterolateral thigh perforator flap.

INTRODUCTION: The reconstruction of extensive three-dimensional defects in the extremities is a difficult challenge. Many attempts have been made to reconstruct such defects using the chimeric flap concept, enabling flaps with larger surface areas to be used while maintaining economical tissue use. The anterolateral thigh (ALT) chimeric flap is one of the most useful tools for the reconstruction of complex three-dimensional defects in the extremities. METHODS: From January 2010 to March 2012, Twenty-two patients underwent extremity reconstruction using chimeric ALT perforator flaps, which consists of a skin component on its isolated perforator and a portion of the fascia and muscle flaps on the same pedicle from the descending branch of the lateral circumflex femoral artery (LCFA). The defects were in either a lower (n = 10) or an upper extremity (n = 12). The area of the soft tissue defects ranged from 43 × 35 cm to 19 × 9 cm (mean, 25 × 18 cm), containing extensive, irregular, ring-like soft tissue defects or degloving injuries. RESULTS: The mean dimension of skin flap was 19.8 × 11.2 cm. The mean dimension of fascia flap was 8.9 × 7.1 cm. The mean dimension of muscle flap was 11.1 × 7.5 cm. No total flap loss occurred. One patient presented with venous thrombosis, and re-anastomosis and vein grafting were performed. Two cases exhibiting partial skin graft loss at the site at which the fascia flap was inset were treated via secondary skin grafts. During a follow-up period of 18 months-30 months, patients were satisfied with the functional and aesthetic outcome. No serious donor-site complications occurred. DISCUSSION: Chimeric anterolateral thigh perforator flap can be one of the best choice for reconstruction of complex soft-tissue defects in the extremities. CONCLUSIONS: The various tissue components and maximal freedom offered by chimeric tissue flaps associated with the same descending branch of the LCFA provide versatile coverage of large, complex, and irregular soft-tissue defects in the extremities.

Jitter characteristic of series magnetic pulse compressor employed in ns trigger generator.

The jitter characteristic of series magnetic pulse compressor (MPC) employed in ns trigger generator was explored. The time delay of the series MPC is the sum value of the compression time in each stage. The primary voltage disturbance is the original parameter to affect the timing stability of the system. Decreasing the relative jitter of the primary voltage and the first compression time are the practical and exclusive approaches to decrease to time jitter of the series MPC. The jitter experiment was carried out on the three-stage series MPC charged with a fast step-up LC transformer. The performance data show that the delay time decreases with the increase of primary voltage. Meanwhile, the measured ratio between the time jitter and the relative jitter of the primary voltage accords with the theoretical result.

Research of an electromagnetically actuated spark gap switch.

As an important part of pulsed power systems, high-voltage and high-current triggered spark gap switch and its trigger system are expected to achieve a compact structure. In this paper, a high-voltage, high-current, and compact electromagnetically actuated spark gap switch is put forward, and it can be applied as a part of an intense electron-beam accelerator (IEBA). A 24 V DC power supply is used to trigger the switch. The characteristics of the switch were measured for N2 when the gas pressure is 0.10-0.30 MPa. The experimental results showed that the voltage/pressure (V/p) curve of the switch was linear relationship. The operating ranges of the switch were 21%-96%, 21%-95%, 21%-95%, 19%-95%, 17%-95%, and 16%-96% of the switch's self-breakdown voltage when the gas pressures were 0.10, 0.14, 0.18, 0.22, 0.26, and 0.30 MPa, respectively. The switch and its trigger system worked steadily and reliably with a peak voltage of 30 kV, a peak current of 60 kA in the IEBA when the pressure of N2 in the switch was 0.30 MPa.