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A model describing the dynamic behavior of a few-mode erbium-doped fiber amplifier (FM-EDFA) is derived using the average inversion level. In that model, when the amplification overlap factor and equivalent area are independent of time, the dynamic behavior of an FM-EDFA is described by a differential equation of the average inversion level. This condition is satisfied for an FM-EDFA with a ring-core erbium-doped fiber (EDF). The derived model is validated in simulations and experiments of transient and frequency responses of a 2-LP mode EDFA with a ring-core EDF.

We have proposed a broadband hybrid light source that combines a super luminescent diode (SLD) and thulium-doped fiber amplifier (TDFA) and operates in the 1.8 µm band. This light source can improve the characteristics of the output spectrum by amplifying the output light of the SLD with TDFA. In this study, we investigate the dependence of the output spectral characteristics of the hybrid broadband light source on the thulium-doped fiber (TDF) length used in the TDFA as well as the output spectra of three newly developed SLDs of 1660, 1690, and 1730 nm bands. In the evaluation of the output bandwidth, there are various definitions of output bandwidth, but we adopted the bandwidth with power density of over −40dBm/0.1nm. This is because it is possible to evaluate in this band with a dynamic range of “30 dB/0.1 nm” by using a general optical spectrum analyzer. The hybrid light source achieves the bandwidth of 332 nm, from 1579 to 1911 nm, and a high total output power of over 15 dBm. The maximum ripple was less than ∼0.1dB, which is similar to the maximum value of that of the SLD, without any deterioration in the ripple characteristics owing to the hybrid configuration of the SLD and TDFA.

IMPORTANCE: Administration of anti–programmed cell death protein 1 (anti–PD-1) is now standard therapy in advanced non–small cell lung cancer (NSCLC). However, immune checkpoint inhibitors, including anti–PD-1, have not been assessed in patients with subclinical disease with advanced NSCLC, and no useful clinical biomarkers have been associated with immune-related adverse events (irAEs) among these patients treated with anti–PD-1. OBJECTIVE: To assess the safety and efficacy of anti–PD-1 treatment in patients with subclinical disease with advanced NSCLC and with or without preexisting autoimmune markers, including rheumatoid factor, antinuclear antibody, antithyroglobulin, and antithyroid peroxidase; and to assess potential clinical biomarkers that may be meaningfully and conveniently associated with clinical benefit or with irAEs following anti–PD-1 treatment. DESIGN, SETTING, AND PARTICIPANTS: This medical records analysis retrospectively evaluated 137 patients who received nivolumab or pembrolizumab monotherapy at Sendai Kousei Hospital in Japan between January 2016 and January 2018. Treatment efficacy and irAEs were evaluated along with candidate factors that may be associated with irAEs. EXPOSURES: Absence or presence of specific autoimmune markers and antibodies before treatment. MAIN OUTCOMES AND MEASURES: Preexisting antibodies and autoimmune markers, progression-free survival (PFS), and irAEs. RESULTS: Of 137 patients with advanced NSCLC, 105 were men, the median age was 68 (range, 36-88) years, 99 underwent nivolumab monotherapy, 38 underwent pembrolizumab monotherapy, and 134 had an Eastern Cooperative Oncology Group performance status of 0 or 1. The median PFS was 6.5 (95% CI, 4.4-12.9) months among patients with examined preexisting antibodies and 3.5 (95% CI, 2.4-4.1) months among patients without, suggesting significantly better prognosis in the former. The hazard ratio for disease progression or death in the presence of the examined preexisting antibodies was 0.53 (95% CI, 0.36-0.79; P = .002). The PFS was significantly longer among patients with any preexisting antibodies than among those without. The examined preexisting antibodies (48 patients [73%]) and rheumatoid factor (26 patients [39%]) were more common among patients who developed irAEs. Multivariate analysis indicated that the presence of the examined preexisting antibodies was independently associated with irAEs (odds ratio, 3.25; 95% CI, 1.59-6.65; P = .001). Skin reactions were more frequent among patients with preexisting rheumatoid factor (47% vs 24%, P = .02), whereas thyroid dysfunction was more frequent among patients with preexisting antithyroid antibodies (20% vs 1%, P < .001). CONCLUSIONS AND RELEVANCE: The presence of the examined preexisting antibodies was associated with clinical benefit and with the development of irAEs in patients with NSCLC treated with nivolumab or pembrolizumab. Thus, the presence of these autoimmune markers may help determine the risk-benefit ratio for individual patients with NSCLC, maximizing therapeutic benefits while minimizing irAEs.

This paper investigates the applicability of a model of a cladding-pumped multicore erbium-doped fiber amplifier (CP-MC-EDFA) that employs the average inversion level of an erbium ion. The model is modified to include the effects of multiple cores for modifications of the background loss coefficient of the pump light. The model is validated experimentally by measurements of the pump power, gain transient, and intercore cross-gain modulation of a cladding-pumped 12-core EDFA in which the pump light is uniformly distributed in the inner cladding. The calculated and measured pump power, gain transient response, and gain change caused by the intercore cross-gain modulation agree well, suggesting the modified model is useful for characterizing a CP-MC-EDFA.

We simulated an improvement in fiber characteristics, specifically the differential modal gain (DMG) and the LP_11 mode wavelength dependent gain (WDG) characteristics. We defined the DMG as the gain difference between the C-band wavelength-division multiplexing signal channels of the LP_01 and LP_11 modes at the shortest wavelength, and WDG was the gain difference between the signal gain of the LP_11 mode at the shortest and longest wavelengths, when the DMG of the LP_01 mode was zero. We achieved this improvement by changing the erbium doping distribution in ring-core erbium-doped fiber (RC-EDF), which has been attracting attention as an amplification medium for a 2-mode (LP_01 and LP_11 modes) erbium-doped fiber amplifier for mode-division multiplexed transmission. We applied an α-th power profile, trapezoid profile, and right and left triangular profiles to the RC-EDF. We found that the DMG value changed from negative to positive despite the value of the LP_11 mode WDG being positive, and confirmed that the DMG could be adjusted by changing the distribution. We show level curve maps of the DMG, LP_11 mode WDG, pump power, and EDF length on the allowable 2-signal-mode area map for inner and outer radius combinations of the RC-EDF, and clarify that it is possible to realize a region that provides high-efficiency amplification with a low DMG of <|0.1|  dB and a low WDG of <0.1  dB. Furthermore, we show that by varying the distribution of the erbium doping concentration, we can greatly change the position of the region on the map of the allowable 2-signal-mode area.

The method for estimating the gain coefficient spectrum of an erbium-doped fiber (EDF) is proposed and demonstrated experimentally. The method employs a net gain–loss measurement that uses the I4_13/2 level pumping of the EDF and the McCumber relation. A formula used to obtain the quotient of the gain and loss coefficient from the net gain–loss measurement is derived to determine the parameter in the McCumber relation. It is confirmed that the gain coefficient spectrum of an EDF estimated with the method coincides with the value estimated using a conventional net gain–loss measurement that employs the I4_11/2 level pumping. The method is successfully applied to an erbium/ytterbium-doped fiber, for which it is impossible to perform a conventional net gain–loss measurement with pumping at the I4_11/2 level of erbium ions because of the absorption transition of ytterbium ions from F2_7/2 to F2_5/2 levels.

In such areas as knowledge discovery, data mining and logical analysis of data, methodologies to find relations among attributes are considered important. In this paper, given a data set (T,F) where T⊆{0,1} denotes a set of positive examples and F⊆{0,1} denotes a set of negative examples, we propose a method to identify decomposable structures among the attributes of the data. We first study computational complexity of the problem of finding decomposable Boolean extensions. Since the problem turns out to be intractable (i.e., NP-complete), we propose a heuristic algorithm in the second half of the paper. Our method searches a decomposable partition of the set of all attributes by using the error sizes of almost-fit decomposable extensions as a guiding measure, and then finds structural relations among the attributes in the obtained partition. Some results of numerical experiment on randomly generated data sets are also reported.

The signal-gain characteristics of tellurite-based erbium-doped fiber amplifiers are clarified based on spectroscopic properties and signal-gain measurements. The potential of tellurite-based erbium-doped fiber for use as a broadband light source is also described.