10 W super-wideband ultra-low-intensity-noise single-frequency fiber laser at 1 µm.

A 10 W super-wideband ultra-low-intensity-noise single-frequency fiber laser (SFFL) at 1 µm is experimentally demonstrated, based on dual gain saturation effects from semiconductors and optical fibers, together with an analog-digital hybrid optoelectronic feedback loop. Three intensity-noise-inhibited units synergistically work, which actualizes a connection of effective bandwidth and enhancement of noise-suppressing amplitude. With the cascade action of the semiconductor optical amplifier and optical fiber amplifier, the laser power is remarkably boosted. Eventually, an SFFL with an output power of 10.8 W and a relative intensity noise (RIN) below -150 dB/Hz at the frequency range over 1 Hz is realized. More meaningfully, within the total frequency range of 10 Hz to 10 GHz exceeding 29 octaves, the RIN is controlled to below -160 dB/Hz, approaching the shot-noise limit (SNL) level. To the best of our knowledge, this is the lowest RIN result of SFFL within such an extensive frequency range, and this is the highest output power of the near-SNL super-wideband SFFL. Furthermore, a linewidth of less than 0.8 kHz, a long-term stable polarization extinction ratio of 20 dB, and an optical signal-to-noise ratio of over 60 dB are obtained simultaneously. This start-of-the-art SFFL has provided a systematic solution for high-power and low-noise light sources, which is competitive for sophisticated applications, such as free-space laser communication, space-based gravitational wave detection, and super-long-distance space coherent velocity measurement and ranging.

Expanding gain bandwidth using ion-hybridized fiber for kHz-linewidth single-frequency fiber lasers at S-, C-, and L-bands: design and performance evaluation.

Single-frequency fiber lasers at S-, C-, and L-bands play a crucial role in various applications such as optical network expansion, high-precision metrology, coherent lidar, and atomic physics. However, compared to the C-band, the S- and L-bands have wavelength deviations and suffer from excited-state absorption, which limits the output performance. To address this issue, a strategy called ion hybridization has been proposed to increase the differences in site locations of rare earth (RE) ions in the laser matrix, thereby achieving a broader gain bandwidth. This strategy has been applied to an Er3+/Yb3+ co-doped modified phosphate fiber (EYMPF), resulting in gain coefficients per unit length greater than 2 dB/cm at S-, C-, and L-bands. To demonstrate its capabilities, several centimeter-long EYMPFs have been used to generate single-frequency laser outputs at S-, C- and L-bands with kHz-linewidths, high signal-to-noise ratios (>70 dB), and low relative intensity noise (<-130 dB/Hz) in a compact short linear-cavity configuration.

Frequency-stabilized improvement of saturated absorption spectroscopy based on laser linewidth-control strategy.

Single-frequency fiber lasers (SFFLs), 1083 nm, have been extensively applied in 4He optical pumping magnetometers (OPMs) for magnetic field detection. However, the sensitivity and accuracy of OPMs are constrained by the frequency stability of SFFLs. Focusing on this concern, the frequency-stabilized performance of the 1083 nm SFFLs is successfully improved by externally tailoring the laser linewidth to match the spectral width of the error signal in saturated absorption spectroscopy. Thereinto, a high-intensity error signal of saturated absorption is generated as a large number of 4He atoms with a wide range of velocities interacting with the 1083 nm laser. Consequently, the root mean square value of the fluctuating frequency after locking is effectively decreased from 24.6 to 13.6 kHz, which achieves a performance improvement of 44.7%. Such a strategy can provide a technical underpinning for effectuating an absolute frequency stabilization with higher precision based on atomic and molecular absorption spectroscopy techniques.

Promoting threshold voltage of P2-Na0.67Ni0.33Mn0.67O2 with Cu2+ cation doping toward high-stability cathode for sodium-ion battery.

P2-type Na0.67Ni0.33Mn0.67O2 has attracted considerable attraction as a cathode material for sodium-ion batteries owing to its high operating voltage and theoretical specific capacity. However, when the charging voltage is higher than 4.2 V, the Na0.67Ni0.33Mn0.67O2 cathode undergoes a detrimental irreversible phase transition of P2-O2, leading to a drastic decrease in specific capacity. To address this challenge, we implemented a Cu-doping strategy (Na0.67Ni0.23Cu0.1Mn0.67O2) in this work to stabilize the structure of the transition metal layer. The stabilization strategy involved reinforcing the transition metal-oxygen (TMO) bonds, particularly the MnO bond and inhibiting interlayer slip during deep desodiation. As a result, the irreversible phase transition voltage is delayed, with the threshold voltage increasing from 4.2 to 4.4 V. Ex-situ X-ray diffraction measurements revealed that the Na0.67Ni0.23Cu0.1Mn0.67O2 cathode maintains the P2 phase within the voltage window of 2.5-4.3 V, whereas the P2-Na0.67Ni0.33Mn0.67O2 cathode transforms entirely into O2-type Na0.67Ni0.33Mn0.67O2 when the voltage exceeds 4.3 V. Furthermore, absolute P2-O2 phase transition of the Na0.67Ni0.23Cu0.1Mn0.67O2 cathode occurred at 4.6 V, indicating that Cu2+ doping enhances the stability of the layer structure and increases the threshold voltage. The resulting Na0.67Ni0.23Cu0.1Mn0.67O2 cathode exhibited superior electrochemical properties, demonstrating an initial reversible specific capacity of 89.1 mAh/g at a rate of 2C (360 mA g-1) and retaining more than 78 % of its capacity after 500 cycles.

Polysaccharides Produced by Plant Growth-Promoting Rhizobacteria Strain Burkholderia sp. BK01 Enhance Salt Stress Tolerance to Arabidopsis thaliana.

Salt stress is one of the most serious abiotic stresses leading to reduced agricultural productivity. Polysaccharides from seaweed have been used as biostimulants to promote crop growth and improve plant resistance to abiotic stress. In this study, PGPR strain Burkholderia sp. BK01 was isolated from the rhizosphere of wheat, and it was characterized for phosphorus (Pi) dissolution, indole-3-acetic acid (IAA) production, ammonia (NH3) and exopolysaccharides (EPS). In particular, strain BK01 can efficiently produce extracellular polysaccharide with a yield of 12.86 g/L, using sorbitol as carbon source. BK01 EPS was identified as an heteropolysaccharide with Mw 3.559 × 106 Da, composed of (D)-galactose (75.3%), (D)-glucose (5.5%), (L)-rhamnose (5.5%), (D)-galactouronic acid (4.9%) and (D)-glucuronic acid (8.8%). The present work aims to highlight the effect of the BK01 EPS on growth and biochemical changes in Arabidopsis thaliana under salt stress (100 mM). The purified BK01 EPS at a concentration of 100 mg/L efficiently promoted the growth of plants in pot assays, improved the chlorophyll content, enhanced the activities of SOD, POD and CAT, and decreased the content of MDA. This results suggested that the polysaccharides produced by PGPR strain Burkholderia sp. BK01 can be used as biostimulants to promote plant growth and improve plant resistance to salt stress.

Single-frequency fiber laser at 1627†nm based on a self-designed Er-doped hybridized glass fiber.

Aiming at applications like expanding usable wave band of optical telecommunication and preparing Sr optical lattice clocks, a 1627 nm single-frequency fiber laser (SFFL) is demonstrated based on a 7-m-long self-designed Er-doped hybridized glass fiber (EDHF) and a linear cavity configuration with a loop mirror filter (LMF). By inserting a 10-m-long unpumped commercial Er-doped fiber as a dynamic Bragg grating into the LMF, a stable single-longitudinal-mode (SLM) laser with an output power of about 10 mW is obtained. The optical signal-to-noise ratio (OSNR) of SFFL is over 50 dB, and the linewidth is about 3.7 kHz. The measured relative intensity noise (RIN) is less than -140 dB/Hz at frequencies of over 0.5 MHz, and a power variation in 1 h is less than ±0.26%. To our best knowledge, it is the first demonstration of a SFFL operating at the U-band. This 1627 nm SFFL can provide advanced light source technology support for many cutting-edge applications.

High-sensitivity hemoglobin detection based on polarization-differential spectrophotometry.

Hemoglobin content is recognized as a momentous and fundamental physiological indicator, especially the precise detection of trace hemoglobin is of great significance for early diagnosis and prevention of tumors, cancer, organic injury, etc. Therefore, high-sensitivity hemoglobin detection is imperative. However, effective detection methods and reliable detection systems are still lacking and remain enormous challenges. Herein, we present a synthetical strategy to break through the existing bottleneck based on polarization-differential spectrophotometry and high-performance single-frequency green fiber laser. Importantly, this framework not only has precisely extracted the two-dimensional information of intensity and polarization during the interaction between laser and hemoglobin, but also has taken advantage of the high monochromaticity and fine directivity in the optimized laser source to reduce the undesirable scattered disturbance. Thus, the hemoglobin detection sensitivity of 7.2 × 10-5 g/L has advanced a hundredfold compared with conventional spectrophotometry, and the responsive dynamic range is close to six orders of magnitude. Results indicate that our technology can realize high-sensitivity detection of trace hemoglobin content, holding promising applications for precision medicine and early diagnosis as an optical direct and fast detection method.

Ultrafine electro-optical frequency comb based on cascade phase modulation with cyclic frequency shifting.

An ultrafine electro-optical frequency comb (EOFC) with plentiful comb teeth is demonstrated. Adopting a single-frequency fiber laser as a light source, cascade phase modulation based on a sinusoidal signal and a frequency-time transformation (FTT) signal is executed to generate the EOFC with high fineness. Meanwhile, a cyclic fast frequency shifting strategy is introduced to boost the number of comb teeth and the bandwidth of the EOFC. As a result, an EOFC with 12600 comb lines covering a broad bandwidth from -6.3 GHz to 6.3 GHz is established, corresponding to an ultrafine comb space of 1 MHz. Moreover, the power fluctuation of a comb tooth is less than 0.5 dBm. This state-of-the-art EOFC has significant potential in the field of precision spectroscopy.

Anti-inflammatory effect of ApoE23 on Salmonella typhimurium-induced sepsis in mice.

Two independent experiments were performed with three groups each (sepsis control, sepsis, and sepsis with apoE23 treatment) to investigate the anti-inflammatory effect of apolipoprotein 23 (apoE23) in a mouse model of sepsis induced by S. typhimurium. Survival rates; plasma level variations in tumor necrosis factor (TNF)-α, interleukin (IL)-6, and lipopolysaccharide (LPS); S. typhimurium colony-forming units in the spleen tissue; and mRNA and protein expression levels of low-density lipoprotein receptor (LDLR), LDLR-related protein (LRP), syndecan-1, and scavenger receptor B1 were evaluated in the livers of mice from the three groups. Results found that the survival rate of septic mice treated with apoE23 was 100% within 48 h, while it was only 40% in septic mice without apoE23 treatment (P < 0.001). The plasma LPS, TNF-α, and IL-6 levels and the S. typhimurium load in mice in the apoE23-treated group were significantly lower than those in septic mice (P < 0.05). Moreover, apoE23 restored the downregulated expression of LDLR and LRP in the liver tissue of septic mice. So apoE23 exhibits an anti-inflammatory effect in the mouse model of S. typhimurium-induced sepsis. Further studies are required to understand the mechanisms underlying the anti-inflammatory effects of apoE23.

Wideband ultra-low intensity noise reduction via joint action of gain saturation and out-of-phase polarization mixing effect from a semiconductor optical amplifier.

In this article, the vector dynamics of semiconductor optical amplifiers (SOAs) are systematically analyzed and developed to explore its mechanism of intensity noise suppression. First, theoretical investigation on the gain saturation effect and carrier dynamics is performed via a vectorial model, and the calculated result unravels desynchronized intensity fluctuations of two orthogonal polarization states. Particularly, it predicts an out-of-phase case, which allows the cancellation of the fluctuations via adding up the orthogonally-polarized components, then establishes a synthetic optical field with stable amplitude and dynamic polarization, and thereby enables a remarkable relative intensity noise (RIN) reduction. Here, we term this approach of RIN suppression as out-of-phase polarization mixing (OPM). To validate the OPM mechanism, we conduct an SOA-mediated noise-suppression experiment based on a reliable single-frequency fiber laser (SFFL) with the presence of relaxation oscillation peak, and subsequently carry out a polarization resolvable measurement. By this means, out-of-phase intensity oscillations with respect to the orthogonal polarization states are clearly demonstrated, and consequently enable a maximum suppression amplitude of >75 dB. Notably, the RIN of 1550-nm SFFL, suppressed by joint action of OPM and gain saturation effect, is dramatically reduced to -160 dB/Hz in a wideband of 0.5 MHz∼10 GHz, and the performance of which is excellent by comparing with the corresponding shot noise limit of -161.9 dB/Hz. The proposal of OPM here not only facilitates us to dissect the vector dynamics of SOA but also offers a promising solution to realize wideband near-shot-noise-limited SFFL.

Differential Brain Expression Patterns of microRNAs Related to Olfactory Performance in Honey Bees (Apis mellifera).

MicroRNAs (miRNAs) play a vital role in the nerve regulation of honey bees (Apis mellifera). This study aims to investigate the differences in expression of miRNAs in a honey bee's brain for olfactory learning tasks and to explore their potential role in a honey bee's olfactory learning and memory. In this study, 12 day old honey bees with strong and weak olfactory performances were utilized to investigate the influence of miRNAs on olfactory learning behavior. The honey bee brains were dissected, and a small RNA-seq technique was used for high-throughput sequencing. The data analysis of the miRNA sequences revealed that 14 differentially expressed miRNAs (DEmiRNAs) between the two groups, strong (S) and weak (W), for olfactory performance in honey bees were identified, which included seven up-regulated and seven down-regulated. The qPCR verification results of the 14 miRNAs showed that four miRNAs (miR-184-3p, miR-276-3p, miR-87-3p, and miR-124-3p) were significantly associated with olfactory learning and memory. The target genes of these DEmiRNAs were subjected to the GO database annotation and KEGG pathway enrichment analyses. The functional annotation and pathway analysis showed that the neuroactive ligand-receptor interaction pathway, oxidative phosphorylation, biosynthesis of amino acids, pentose phosphate pathway, carbon metabolism, and terpenoid backbone biosynthesis may be a great important pathway related to olfactory learning and memory in honey bees. Our findings together further explained the relationship between olfactory performance and the brain function of honey bees at the molecular level and provides a basis for further study on miRNAs related to olfactory learning and memory in honey bees.

Self-assembled nanoflower-like FeSe2/MoSe2 heterojunction anode with enhanced kinetics for superior-performance Na-ion half/full batteries.

Transition metal selenides are a research hotspot in sodium-ion batteries (SIBs). However, slow kinetics and rapid capacity decay due to volume changes during cycling limit their commercial applications. Heterostructures have the ability to accelerate charge transport and are widely used in energy storage devices due to their abundant active sites and lattice interfaces. A rational design of heterojunction electrode materials with excellent electrochemical performance is essential for SIBs. Herein, a novel anode material heterostructured FeSe2/MoSe2 (FMSe) nanoflower for SIBs was successfully prepared through a facile co-precipitation and hydrothermal route. The as-prepared FMSe heterojunction exhibits excellent electrochemical performance, including a high invertible capacity (493.7 mA h g-1 after 150 cycles at 0.2 A g-1), long-term cycling stability (352.2 mA h g-1 even after 4200 cycles at 5.0 A g-1) and competitive rate capability (361.2 mA h g-1 at 20 A g-1). By matching with a Na3V2(PO4)3 cathode, it can even exhibit ideal cycling stability (123.5 mA h g-1 at 0.5 A g-1 after 200 cycles). Furthermore, the sodium storage mechanism of the FMSe electrodes was systematically determined by ex situ electrochemical techniques. Theoretical calculation also reveals that the heterostructure on the FMSe interface enhances charge transport and promotes reaction kinetics.

Simultaneous achievement of power boost and low-frequency intensity noise suppression in a bidirectional pumping fiber amplifier based on saturated even-distribution gain.

An optimized bidirectional pumping fiber amplifier is demonstrated to achieve low-frequency intensity noise suppression and effective power enhancement simultaneously. Based on the concept analysis of the gain saturation effect, the influence of input signal power and pump power on intensity noise suppression is investigated and optimized systematically. Further combining with the optimization of the pumping configuration to achieve the even-distribution gain, the relative intensity noise (RIN) of 1083 nm single-frequency fiber laser (SFFL) is suppressed with 9.1 dB in the frequency range below 10 kHz. Additionally, the laser power is boosted from 10.97 dBm to 25.02 dBm, and a power instability of ±0.31% is realized. This technology has contributed to simultaneously improving the power and noise performance of the 1083 nm SFFL, which can be applied to a multi-channel helium (He) optically pumping magnetometer. Furthermore, this technique has broken the mindset that power amplification of the conventional fiber amplifiers will inevitably cause the degradation of intensity noise property, and provided a valuable guidance for the development of high-performance SFFLs.

Astaxanthin Promotes the Survival of Adipose-Derived Stem Cells by Alleviating Oxidative Stress via Activating the Nrf2 Signaling Pathway.

The survival of free fat grafts is dependent primarily on adipose-derived stem cells (ADSCs); however, ADSCs are susceptible to oxidative stress in the recipient area. Astaxanthin (Axt) is a natural xanthophyll carotenoid with potent antioxidant properties and numerous clinical applications. To date, the therapeutic potential of Axt in fat grafting has not been explored. The purpose of this study is to investigate the effects of Axt on oxidatively stressed ADSCs. An oxidative model of ADSCs was developed to simulate the host's microenvironment. Oxidative insult decreased the protein levels of Cyclin D1, type I collagen alpha 1 (COL1A1), and type II collagen alpha 1 (COL2A1), while increasing the expression of cleaved Caspase 3 and secretion of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in ADSCs. Axt pre-treatment significantly reduced oxidative stress, increased the synthesis of an adipose extracellular matrix, alleviated inflammation, and restored the impaired adipogenic potential in the present model. Furthermore, Axt immensely activated the NF-E2-related factor 2 (Nrf2) pathway, and ML385, an inhibitor of Nrf2, could negate Axt's protective effects. Additionally, Axt alleviated apoptosis by inhibiting bcl-2-associated X protein (BAX)/Caspase 3 signaling and improving the mitochondrial membrane potential (MMP), which could also be abolished by ML385. Our results suggest that Axt may exert its cytoprotective effect on ADSCs through the Nrf2 signaling pathway and could be therapeutic in fat grafting.

SurvivalPath:A R package for conducting personalized survival path mapping based on time-series survival data.

The survival path mapping approach has been proposed for dynamic prognostication of cancer patients using time-series survival data. The SurvivalPath R package was developed to facilitate building personalized survival path models. The package contains functions to convert time-series data into time-slices data by fixed interval based on time information of input medical records. After the pre-processing of data, under a user-defined parameters on covariates, significance level, minimum bifurcation sample size and number of time slices for analysis, survival paths can be computed using the main function, which can be visualized as a tree diagram, with important parameters annotated. The package also includes function for analyzing the connections between exposure/treatment and node transitions, and function for screening patient subgroup with specific features, which can be used for further exploration analysis. In this study, we demonstrate the application of this package in a large dataset of patients with hepatocellular carcinoma, which is embedded in the package. The SurvivalPath R package is freely available from CRAN, with source code and documentation hosted at https://github.com/zhangt369/SurvivalPath.

Engineering crystal-facet modulation to obtain stable Mn-based P2-layered oxide cathodes for sodium-ion batteries.

The undesirable phase transformation of Mn-based P2-layered oxide cathodes is a tremendous challenge in commercializing Mn-based oxide cathodes for sodium-ion batteries. In this work, Na0.67MnO2 cathode with stable P2-type structure was successfully synthesized by modulating its coordination numbers to suppress the preferred orientation growth of (001) crystal plane, which was realized to maintain a stable P2-type structure in the whole state of charging and discharging. Specifically, designing Mn2+ six coordination sites to lower the high surface energy of (001) crystal plane is an effective way to reduce nucleation rates, which leads to the production of few grain boundaries and the suppression of layer-to-layer stacking in the crystal growth stage. Due to their fewer grain boundaries and skeleton structure with layer-to-layer stacking, the interlaminar stress and intragranular fatigue cracks can be alleviated in the long-life cycling performance of Na0.67MnO2 cathode. Na0.67MnO2 cathodes derived from the precursor of Mn2+ six coordination sites (C-Na0.67MnO2) have more exposed {010} crystal face and enlarged sodium-ion diffusion channels and structure integrity compared to Na0.67MnO2 cathode prepared by the precursor of Mn2+ four coordination sites (O-Na0.67MnO2). Therefore, C-Na0.67MnO2 cathode delivers an initial capacity of 106.8 mAh/g and has excellent capacity retention of 94.8 % after 150 cycles at 80 mAh/g. The rational design strategy endows Mn-based P2-layered oxide cathodes with stable sodium-ion diffusion channels and lamellar structure.

Pulse compression of a single-frequency Q-switched fiber laser based on the cascaded four-wave mixing effect.

A pulse compressing technology of single-frequency Q-switched laser based on the cascaded four-wave mixing (CFWM) effect is demonstrated theoretically and experimentally, for the first time to the best of our knowledge. A theoretical model of the pulse compression is established through deconstructing the pulse duration evolution in the high-order Stokes and anti-Stokes lights of CFWM. A pulse compression ratio of (2|m|+1)1/2 is quantificationally obtained with m corresponding to the order number of the CFWM light. Utilizing dual-wavelength (DW) single-frequency Q-switched laser injected into a highly nonlinear fiber (HNLF), the pulse compression and the spectral broadening phenomenon are observed simultaneously. As the order number of the CFWM light increases from 0-order to 3-order, the pulse duration has reduced from 115 ns to 47 ns with a compression ratio of 2.45, which is essentially consistent with the theoretical analysis. The pulse compressing technique by CFWM is conducive to promoting the performance development of the single-frequency Q-switched laser, which can improve the system precision in the Lidar, trace gas detection, and high-precision ranging. Furthermore, this technology based on time-frequency transformation dynamics may be generally applicable to other single-frequency pulsed fiber lasers.

Over-20-octaves-bandwidth ultralow-intensity-noise 1064-nm single-frequency fiber laser based on a comprehensive all-optical technique.

An over-20-octaves-bandwidth ultralow-intensity-noise 1064-nm single-frequency fiber laser (SFFL) is demonstrated based on a comprehensive all-optical technique. With a joint action of booster optical amplifier (BOA) and reflective Yb-doped fiber amplifier (RYDFA), two-fold optical gain saturation effects, respectively occurring in the media of semiconductor and fiber, have been synthetically leveraged. Benefiting from the gain dynamics in complementary time scales, i.e., nanosecond-order carrier lifetime in BOA and millisecond-order upper-level lifetime in RYDFA, the relative intensity noise (RIN) is reduced to -150 dB/Hz from 0.2 kHz to 350 MHz, which exceeds 20-octaves bandwidth. Remarkably, a maximum suppressing ratio of >54 dB is obtained, and the RIN in the range of 0.09-10 GHz reaches -161 dB/Hz which is only 2.3 dB above the shot-noise limit. This broad-bandwidth ultralow-intensity-noise SFFL can serve as an important building block for squeezed light generation, space laser communication, space gravitational wave detection, etc.

New dual-function in situ bone repair scaffolds promote osteogenesis and reduce infection.

BACKGROUND: The treatment of infectious bone defects is a difficult problem to be solved in the clinic. In situ bone defect repair scaffolds with anti-infection and osteogenic abilities can effectively deal with infectious bone defects. In this study, an in situ polycaprolactone (PCL) scaffold containing ampicillin (Amp) and Mg microspheres was prepared by 3D printing technology. RESULTS: Mg and Amp were evenly distributed in PCL scaffolds and could be released slowly to the surrounding defect sites with the degradation of scaffolds. In vitro experiments demonstrated that the PCL scaffold containing Mg and Amp (PCL@Mg/Amp) demonstrated good cell adhesion and proliferation. The osteogenic genes collagen I (COL-I) and Runx2 were upregulated in cells grown on the PCL@Mg/Amp scaffold. The PCL@Mg/Amp scaffold also demonstrated excellent antibacterial ability against E. coli and S. aureus. In vivo experiments showed that the PCL@Mg/Amp scaffold had the strongest ability to promote tibial defect repair in rats compared with the other groups of scaffolds. CONCLUSIONS: This kind of dual-function in situ bone repair scaffold with anti-infection and osteogenic abilities has good application prospects in the field of treating infectious bone defects.

All-fiber mode-locked gigahertz femtosecond laser at 1610 nm using a self-developed long-wavelength gain fiber.

We report a compact all-fiber passively mode-locked ultrafast laser with a fundamental repetition rate of 1.6 GHz that uses a self-developed long-wavelength active fiber, i.e., a fluoro-sulfo-phosphate-based Er3+/Yb3+ co-doped fiber (only 6.2 cm in length). This active fiber can provide a net gain coefficient of 0.6 dB/cm at 1610 nm. The high-repetition-rate all-fiber mode-locked laser operates at a low pump power of only approximately 90 mW. The mode-locked pulse train has a period of 625 ps and a 3 dB bandwidth of 7.0 nm, which can support a transform-limited pulse width of 390 fs.