Effect of Noise Distribution in a WDM System Seeded by a Spectrum-Sliced ASE

Sang-Rok Moon,Sang-Hwa Yoo,Chang-Hee Lee IEEE 2014 Journal of Lightwave Technology Vol.32 No.12

<P>We investigate the impact of noise distribution on the bit error rate (BER) in a WDM system seeded by a spectrum sliced amplified spontaneous emission. The Gamma distribution of the intensity noise was considered for accurate estimation of transmission performance in a real system. The power penalty by the relative intensity noise and the extinction ratio (ER) were calculated to identify a suitable operation range. To consider the finite ER, numerical simulation was conducted. We also investigate change of the noise distribution after noise suppression and fiber transmission, and the effect on the BER by the distribution change.</P>

응급진료센터 과밀화와 특별관찰구역의 운영

심호식,장문준,하영록,정순미,이한식 大韓應急醫學會 1997 대한응급의학회지 Vol.8 No.1

Overcrowding of emergency departments is a growing problem. Delays in admitting patients to inpatient units have been reported as a contributing factor to overcrowding. Overcrowding in ED results in many patients not receiving needed care and impairs the ability of the ED provider to meet the needs of those patients that are treated. The effect of the critically ill patients on the overcrowded emergency department make emergency physicians frustrated. So we created the 'special unit for observation' of critically ill patients and managed them continuously and closely. The special unit for observation have 4 physical beds and monitors and 2 ventilators. One nurse and senior ED residents were asigned to the management of the patients in the special unit. 160 patients(3.4% of all ED visits) admitted to special unit during the period of March 1, 1996 to May 31, 1996. we could continue assessment and management of critically ill patients without psychologic strain or burnout generated by overcrowding. We think that special unit for critically ill patients is a very effective alternative to overcrowded ED.

Feed Forward Noise Suppression for ASE-Seeded WDM Systems

Sang-Rok Moon,Sang-Hwa Yoo,Myeonggyun Kye,Chang-Hee Lee IEEE 2016 Journal of Lightwave Technology Vol.34 No.9

<P>We investigate feed forward noise suppression for ASE-seeded WDM systems in relation to its limitations. In particular, limitation factors such as background ASE of reflective light sources and filtering effect are thoroughly investigated. We also measure the penalty induced by feed forward parameter variation from the designed value. Although the BER performance is improved by noise suppression, the statistical noise distribution change reduces the effectiveness of noise suppression.</P>

Anterior Cervical Instrumentation Using Intradiscal Cage with Integrated Plate

Ahn, Kyoung-Rok,Ryu, Kyeong-Sik,Chang, In-Bok,Cho, Byung-Moon,Park, Se-Hyuck,Oh, Sae-Moon The Korean Neurosurgical Society 2006 Journal of Korean neurosurgical society Vol.39 No.4

Objective : The retrospective study is undertaken to report clinical results of anterior cervical interbody fusion with an intradiscal cage with an integrated plate [PCB cervical plating system]. Methods : 38 patients underwent anterior cervical interbody fusion with PCB cervical plating system and followed $6{\sim}24\;months$. The authors investigated overall surgical results; clinical outcome, fusion rate, change of interspace height & lordotic angle, and complications. Results : No complication was observed during the operation. Clinical improvement was identified in 34 cases [89.5%]. Bone fusion observed in 44 out of 49 sites [90.7%]. After operation, the interspace height increased from $5.4{\pm}1.3mm$ to $7.8{\pm}1.5mm$ and maintained $7.4{\pm}1.1mm$ and, interspace angle went up from $4.2{\pm}0.7^{\circ}$ to $4.8{\pm}1.1^{\circ}$ and maintained $4.6{\pm}$0.9^{\circ}. The loosening of screw was observed in 6 cases, one of which had reoperation because of the expulsion of the device accompanied. Conclusion : PCB cervical plating system could restore interbody height and lordosis in anterior cervical interbody fusion. But, if the insertion of the spacer is not precise, the frequencies of hardware failure are relatively high. It is considered necessary for the operator to be careful in the procedure.

Effects of Lowering Dialysate Calcium Concentrations on Arterial Stiffness in Patients Undergoing Hemodialysis

( Jwa Kyung Kim ),( Sung Jin Moon ),( Hyeong Cheon Park ),( Jae Sung Lee ),( Soung Rok Sim ),( Sung Chang Bae ),( Sung Kyu Ha ) 대한내과학회 2011 The Korean Journal of Internal Medicine Vol.26 No.3

Background/Aims: We assessed changes in hemodynamic and arterial stiffness parameters following reductions of dialysate calcium concentrations in patients undergoing hemodialysis. Methods: In this prospective study, 20 patients on maintenance hemodialysis (10 females, 10 males) with dialysate calcium concentrations of 1.75 mmol/L were enrolled. At the start of the study, the dialysate calcium level was lowered to 1.50 mmol/L. Serial changes in biochemical, hemodynamic, and arterial stiffness parameters, including pulse wave velocity (PWV) and augmentation index (AIx), were assessed every 2 months for 6 months. We also examined changes in the calcification-inhibitory protein, serum fetuin-A. Results: During the 6-month study period, serum total calcium and ionized calcium decreased consistently (9.5 ± 1.0 to 9.0 ± 0.7, p = 0.002 vs. 1.3 ± 0.1 to 1.1 ± 0.1, p = 0.035). Although no apparent changes in blood pressure were observed, heart-femoral PWW (hf-PWV) and AIx showed significant improvement (p = 0.012, 0.043, respectively). Repeatedmeasures ANOVA indicated a significant effect of lowering dialysate calcium on hf-PWV (F = 4.58, p = 0.004) and AIx (F = 2.55, p = 0.049). Accompanying the change in serum calcium, serum fetuin-A levels significantly increased (95.8 ± 45.8 pmol/mL at baseline to 124.9 ± 82.2 pmol/mL at 6 months, p = 0.043). Conclusions: Lowering dialysate calcium concentration significantly improved arterial stiffness parameters, which may have been associated with upregulation of serum fetuin-A.

Delayed Burr Hole Surgery in Patients with Acute Subdural Hematoma : Clinical Analysis

Choi, Yoon Heuck,Han, Seong Rok,Lee, Chang Hyun,Choi, Chan Young,Sohn, Moon Jun,Lee, Chae Heuck The Korean Neurosurgical Society 2017 Journal of Korean neurosurgical society Vol.60 No.6

Objective : To evaluate the effectiveness and efficacy of delayed burr hole surgery in relation to the reduction of postoperative subdural hematoma (SDH) volume in patients with acute SDH. Methods : We retrospectively analyzed patients with acute SDH who received delayed burr hole surgery at our institute. Age, sex, Glasgow coma scale, maximal SDH thickness, volume of SDH, midline shifts, hounsfield unit (HU), and medical history of anticoagulant agent usage were recorded. Outcome measures were delayed operation day, reduction of SDH volume after operation, and the Glasgow outcome scale (GOS) score at discharge. The patients were divided two groups according to the postoperative reduction of volume of SDH (${\geq}50%$, group A; <50%, group B). We also analyzed variables and differences between two groups. Results : Eighteen patients were available for this analysis. The mean delayed of surgery was $13.9{\pm}7.5$ days. Maximal thickness of SDH was changed from $10.0{\pm}3.5mm$ to $12.2{\pm}3.7mm$. Volume of SDH was changed from $38.7{\pm}28.0mL$ to $42.6{\pm}29.6mL$. Midline shifts were changed from $5.8{\pm}3.3mm$ to $6.6{\pm}3.3mm$. HU were changed from $66.4{\pm}11.2$ to $53.2{\pm}20.6$. Post-operative reduction of SDH volume was $52.1{\pm}21.1%$. Eleven patients (61%) had a discharge GOS score of 1 (good recovery). Ten patients (56%) were enrolled in group A. Midline shifting was greater in group A than in group B ($7.4{\pm}3.3$ vs. $3.0{\pm}2.4mm$; p<0.02). The delay of surgery was shorter for group A than group B ($9.2{\pm}2.3$ vs. $19.8{\pm}7.7$ days; p<0.0008). Conclusion : Among well selected patients, delayed burr hole surgery in patients with acute SDH may be effective for reduction of SDH volume. Further studies will be necessary to establish the effectiveness and safety of delayed burr hole surgery in patients with acute SDH.

All-fiber 6-mode multiplexers based on fiber mode selective couplers

Chang, Sun Hyok,Moon, Sang-Rok,Chen, Haoshuo,Ryf, Roland,Fontaine, Nicolas K.,Park, Kyung Jun,Kim, Kwangjoon,Lee, Joon Ki The Optical Society 2017 Optics express Vol.25 No.5

<P>All-fiber 6-mode multiplexer composed of two consecutive LP11-mode selective couplers (MSC), two LP21-MSCs and an LP02-MSC is fully characterized by wavelength-swept interferometer technique. The MSCs are fabricated by polished-type fiber couplers coupling LP01 mode of a single mode fiber into a higher-order mode of a few mode fiber. A pair of the mode multiplexers has minimum mode dependent loss of 4 dB and high mode group selectivity of over 15 dB. Mode division multiplexed transmission enabled by the all-fiber mode multiplexers is demonstrated over fiber spans of 117 km employing an in-line multi-mode optical amplifier. 6 modes of 120 Gb/s dual polarization quadrature phase shift keying signals combined with 30 wavelength channels are successfully transmitted. (C) 2017 Optical Society of America</P>

CFO compensation method using optical feedback path for coherent optical OFDM system

Moon, Sang-Rok,Hwang, In-Ki,Kang, Hun-Sik,Chang, Sun Hyok,Lee, Seung-Woo,Lee, Joon Ki Elsevier 2017 Optical fiber technology Vol.36 No.-

<P><B>Abstract</B></P> <P>We investigate feasibility of carrier frequency offset (CFO) compensation method using optical feedback path for coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. Recently proposed CFO compensation algorithms provide wide CFO estimation range in electrical domain. However, their practical compensation range is limited by sampling rate of an analog-to-digital converter (ADC). This limitation has not drawn attention, since the ADC sampling rate was high enough comparing to the data bandwidth and CFO in the wireless OFDM system. For CO-OFDM, the limitation is becoming visible because of increased data bandwidth, laser instability (i.e. large CFO) and insufficient ADC sampling rate owing to high cost. To solve the problem and extend practical CFO compensation range, we propose a CFO compensation method having optical feedback path. By adding simple wavelength control for local oscillator, the practical CFO compensation range can be extended to the sampling frequency range. The feasibility of the proposed method is experimentally investigated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> For CO-OFDM system, the CFO compensation range is limited by sampling rate of ADC. </LI> <LI> CFO compensation method using optical feedback path is proposed. </LI> <LI> This technique can be applied if receiver bandwidth is limited. </LI> <LI> This technique can be applied for all coherent modulation formats. </LI> </UL> </P>

Automatic wavelength allocation method using Rayleigh backscattering for a WDM-PON with tunable lasers

Sang-Rok Moon,Hoon-Keun Lee,Chang-Hee Lee IEEE 2013 Journal of optical communications and networking Vol.5 No.3

<P>We propose an automatic wavelength control method using Rayleigh backscattering in a feeder fiber for tunable lasers employed in a wavelength-division multiplexing passive optical network. We demonstrate two realization methods, maximizing backscattered power and maximizing the second harmonic component with wavelength modulation. We analyze their limiting factors and impacts on the system performance. We use a VCSEL as a low-cost tunable light source.</P>

Feed Forward Noise Suppression in Injection Seeded WDM-PON With ASE

Sang-Rok Moon,Joon-Young Kim,Chang-Hee Lee IEEE 2012 IEEE Photonics Technology Letters Vol.24 No.15

<P>We propose a noise suppression method using a feed forward circuit for injection-seeded WDM-PON. The required injection power is reduced by 8 dB by employing the proposed method. We investigate the limiting factors by tracing the relative intensity noise in the injection-seeded WDM-PON. Interplay of two filtering effects determines the net suppression of noise.</P>