We report the calculation of beginning-of-life and end-of-life (EOL) optical signal-to-noise ratio (OSNR) margins in designs of 10,000 km terrestrial and subsea Pb/s capacity all-optical (without O-E-O regeneration) dense wavelength division multiplexed lightwave systems in the 2000 nm band. Our margin analysis follows the OSNR budget tables originally designed for 1550 nm subsea lightwave transmission systems employing erbium-doped fiber amplifiers, as adapted for novel hybrid Tm-Ho-doped fiber amplifiers and hollow core fibers designed to operate in the 2000 nm region off the spectrum. Our analysis shows that ideal simulated losses of ≤ 0.0325 dB/km at 2000 nm in the novel hollow core transmission fibers are required for successful EOL system operation in the terrestrial lightwave system design, when assuming that the effective deployed loss = ideal loss + 0.030 dB/km. We discuss the implications of this analysis in the context of terminal tolerances, manufacturing and environmental impairments, Q-factor time variations, customer margins, and the anticipated aging behavior of the novel 2000 nm hollow core transmission fiber. Received: 15 May 2025 | Revised: 29 July 2025 | Accepted: 28 August 2025 Conflicts of Interest The author declares that he has no conflicts of interest to this work. Data Availability Statement Data for the 700 mW 1190 nm fiber-coupled PM-packaged pump diode are openly available at https://www.innolume.com/fabry-perot-laser-diodes/fiber-coupled-single-mode-laser-diode-at-1195nm-5/. Other data are available from the corresponding author upon reasonable request. Author Contribution Statement Robert E. Tench: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Resources, Data curation, Writing – original draft, Writing – review & editing, Visualization, Supervision, Project administration, Funding acquisition.

We report the experimental performance of a tunable polarization-maintaining (PM) holmium-doped fiber ring laser, followed by a single-clad single-stage holmium-doped fiber amplifier. An average output power of 1.6 W over a tuning range of 100 nm (from 2000 to 2100 nm) was obtained for 6.5 W of total launched pump power at 1860 nm, corresponding to an optical-to-optical efficiency of 32 %. We measured an optical signal-to-noise ratio (OSNR) larger than 42 dB/0.05 nm and a polarization extinction ratio (PER) larger than 19.6 dB. The long-term power stability exhibited a peak-to-peak variation of 1.2 % over 2 h, and the experimentally measured spectral width of the laser was 530 MHz.

We report the optical architecture, experimental performance, and simulated performance of polarization- maintaining CW and pulsed single clad Tm-doped fiber amplifiers designed to operate over a wavelength span of 1760-1960 nm. We highlight the potential applications of these amplifiers to quantum computing and quantum qubit experiments using 1762 nm light. Our amplifier exhibits 3 W CW output power and 20 W peak pulsed output power (2 MHz rep. rate, 10% duty cycle) at 1762 nm. Measurements of the wavelength response of the TDFA yield an experimental operating bandwidth extending from < 1750 nm to > 1920 nm. Simulations of the amplifier bandwidth indicate a 3 dB (50% FWHM) wavelength span of 1745 nm to 1980 nm (135 nm). Experimental output power and bandwidth results agree well with the simulations. The external noise figure for this amplifier ranges from 7.5 dB to 9.5 dB. No linewidth broadening was observed in a typical TDFA output when using a single frequency input laser source with a linewidth of 10 kHz. We discuss suitability and applications of the TDFA to 1762 nm enabled manipulation of optical qubits in trapped Ba-133(+) ions.

We present the design and experimental and simulated results for a 2050 nm band fiber amplifier with high optical-optical slope efficiency and low ion pairing, using a novel high performance single clad Ho-doped fiber from the Naval Research Laboratory (NRL). We report a measured optical-optical slope efficiency of 57% using 1 mW input signal power and 1860 nm pumping which we believe is the highest slope efficiency measured to date for a single clad copumped HDFA. This efficiency is linked to a low ion pairing coefficient of 4% in the doped fiber derived from our data.

We report the design and demonstration of novel 2 μm band Watt-level fiber amplifiers, fiber lasers, and wideband ASE sources that are pumped with broad spectrum Watt-level ASE sources instead of conventional fiber laser pumps. We show good agreement between the simulations and experimental results for the performance of a single-stage Ho-doped fiber amplifier at 2050nm wavelength pumped by a 50 nm broadband Tm-doped ASE source centered at 1860 nm. Next, we show that the new ASE pumping approach works effectively for a two -stage Ho-doped fiber amplifier as for a single stage Ho-doped fiber amplifier. Then, we demonstrate successfully the pumping of a Tm-doped fiber laser at 2039 nm using an ASE source centered at 1550 nm. Finally, we produce a novel 265 nm wide broadband ASE source at 2 μm by concatenating Tm and Ho ASE sources. Our ASE-based pumping approach is simple and versatile compared to the standard laser based pumping means, and leads to similar device performance.

We demonstrate ASE pumping of rare-earth-doped fiber amplifiers, fiber lasers, and broadband ASE sources. Pumping with an ASE source yields the advantages of optical-optical efficiencies comparable to conventional pumps, generation of ultra-broad-band ASE sources, and reduced low frequency noise transferred from the pump to the signal.

We report the design and applications of a novel multi-Watt (>1Watt output power) 2000 nm band hybrid Thulium- and Holmium-doped fiber amplifier with record wideband 380 nm (31.5 THz) continuously operating bandwidth from 1720 to 2100 nm. We outline the theory, physics, and simulations behind this design and show by comparison with previously published experimental results that the design presented is accurate to within ±0.5 dB in saturated output power and ±1.0 dB in small signal gain. Applications in future ∼300–400 nm bandwidth wideband 2000 nm Pb/s DWDM lightwave fiber optical transmission systems spanning 10,000 km using new hollow-core fiber designs are discussed. In particular, we demonstrate robust beginning-of-life optical signal-to-noise ratio and Q-factor margins for designs of 0.161 Pb/s DWDM unregenerated (without optical-to-electrical-to-optical or O-E-O electronic functions) all-optical transmission in the 2000 nm band over 10,000 km for representative terrestrial and submarine lightwave applications. We achieve a total capacity × distance product of 1608 Pb/s. km (1.61 Exabits/s. km) over a single one-core optical fiber for the 10,000 km system designs. Applications to designs of 40,000 km deployable unregenerated all-optical DWDM 0.124 Pb/s subsea lightwave transmission systems with 5.21 Exabit/s. km capacity ×distance product are outlined. Received: 9 September 2024 | Revised: 10 December 2024 | Accepted: 26 December 2024 Conflicts of Interest The author declares that he has no conflicts of interest to this work. Data Availability Statement Exail Tm- and Ho-doped gain fiber specifications are openly available at https://cybel-llc.com/wp-content/uploads/2021/06/IXF-HDF-PM-8-125_edA-Ho-SC-doped-PM-fiber.pdf and https://cybel-llc.com/wp-content/uploads/2021/06/IXF-TDF-PM-5-125_edA-Tm-SC-doped-PM-fiber.pdf. Data of the component devices in Table 1 are openly available at https://retandassociatesllc.com/wp-content/uploads/2024/04/GSLEOP2022-Presentation-RET-v.11-08222022.pdf. Other data are available from the corresponding author upon reasonable request. Author Contribution Statement Robert E. Tench: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Resources, Data curation, Writing - original draft, Writing - review & editing, Visualization, Supervision, Project administration, Funding acquisition.

We report the design, optical architecture, and performance of a packaged tunable all polarization-maintaining (PM) Thulium-doped fiber laser (TDFL) with a continuous tuning range of 1890-2050 nm. It consists of a ring-cavity tunable fiber laser source followed with a booster stage which yields output power >3 W and a linewidth of <0.05 nm (4 GHz). Measured performance in terms of output power (up to 3.6 W), output OSNR (47-53 dB/0.1 nm), and long term power stability (<4% p -p) is presented as a function of wavelength over the full 160 nm tuning range. Applications to characterization of passive and active devices and components in the 2 mu m band are demonstrated.

We report the performance of a CW single-clad PM Tm-doped fiber amplifier optimized for the wavelength band from 1760 to 1960 nm. Output powers as high as 3 W and an OSNR > 55 dB/0.1 nm are achieved with our OEM packaged amplifier.

We present the design and performance of novel, highly stable, broadband, packaged single mode Tm-doped and Ho-doped ASE sources in the 2000 nm spectral band. Centroid wavelengths of 1850–1900 nm are achieved for Tm-doped sources and ~2070 nm for Ho-doped sources. Measured -10 dB spectral bandwidths exceed 100 nm for the Tm-doped sources and 60 nm for the Ho-doped sources. Output powers for two stage Tm-doped sources exceed 1 W CW.

We report the results of gamma radiation testing of the performance of 1064 nm packaged butterfly single mode DFB lasers (QD Laser QLD1061) for satellite and space applications. Both passive and active tests were conducted, with measurements of output power, optical signal-to-noise-ratio (OSNR), output spectra, and polarization extinction ratio (PER) as a function of dose rates and total radiation exposure. No significant changes in laser behavior were observed for total doses up to 100 kRad.

Highly stable, high peak output power pulsed transmitter sources in the 2000 nm band are essential seed lasers for diverse applications such as LIDAR, ground-to-space optical communications, detection of trace gases in the atmosphere, medical applications, and pumping optical parametric oscillators and supercontinuum sources. Previous work utilizing single clad, single mode fibers has demonstrated pulsed mode operation of an optically amplified source at 2051 nm and 2090 nm with pulse widths ranging from 5–500 ns, pulse repetition frequencies (PRFs) of 20–300 kHz, and peak output pulse energies of 10 μJ. In this paper, we report the design and performance of a novel nanosecond MOPA optical transmitter at a signal wavelength of 2070 nm with more than 250 W peak output power and highly stable output pulses. The seed laser is broadened using a phase modulator, to minimize the onset of optical nonlinearities such as SBS and MI and then amplified using a two-stage Ho-doped fiber amplifier (HDFA) employing 8-μm core active fiber. The amplified signal is then transmitted through a tandem arrangement with a 250 MHz acousto-optic modulator (AOM) followed by a high-speed electro-optic amplitude modulator (EOM). This pulses signal is then reamplified by a two-stage HDFA where the second stage employs a 20-μm core active fiber, which reduces the threshold for the onset of nonlinear effects such as modulation instability (MI) and four-wave mixing. We present a comparison of optical simulation results with experimental data for the medium- and large-core Ho-doped fibers in the MOPA transmitter.

We report broadband experimental and simulated performance of a single-clad polarization-maintaining (PM) thulium-doped fiber amplifier (TDFA) optimized for operation in the 1750–1910 nm wavelength band. With the two-stage amplifier architecture, a maximum output power of 2.4 W was obtained at 1850 nm for 7.0 W of launched pump power at 1567 nm, with a corresponding optical-to-optical efficiency of 31.4 %. The measured polarization extinction ratio (PER) was larger than 22.6 dB, and the long-term power stability exhibited a peak-to-peak variation of 2.4 %. By employing a tunable seed laser covering the 1750–1910 nm wavelength range, we measured a maximum output power level of 2.38 W with an optical signal-to-noise ratio (OSNR) greater than 53 dB/0.1 nm. Our simulations are in good agreement with the experimental data over the whole 160 nm operating spectral bandwidth.

We report the design and demonstration of novel 2050 nm Watt-level Ho-doped fibre amplifiers that are pumped with broad spectrum Watt-level Tm-doped ASE sources centred at 1860 nm instead of conventional narrow linewidth semiconductor or fibre laser sources. Our approach is simpler and more cost effective than the standard laser based pumping means, and leads to similar amplifier performance.

We demonstrate the performance of a 2039 nm PM DFB FBG laser pumped with two types of 1.5 µm pumps. We obtained output signal powers >330 mW, with slope efficiency >16%, and a single-mode operation with OSNR >65 dB/0.1 nm. Laser linewidth <12 kHz and the RIN<-117 dB/Hz were measured.

We report the design, optical architecture, and performance of a multi-watt tunable polarization-maintaining Tm-doped fiber laser that can be tuned from 1890—2050 nm. The compact OEM laser exhibits peak fiber coupled output powers of > 3.5 W CW and a linewidth of < 0.05 nm. Data as a function of output wavelength are presented for the output spectrum, output power, OSNR, and long term power stability.

We report the design and performance of medium slope efficiency (64%) Holmium-doped fiber amplifiers (HDFAs) with novel alternative in-band pump wavelengths in the 1720–2000 nm spectral region. We demonstrate through simulations that pump wavelengths of 1840–1860 nm can yield significantly improved output power, gain, and optical-optical conversion efficiency compared to the previous technical and industry standard pump wavelength of 1940 nm. Our simulations are verified by experimental data.

We report the design and performance of a 2 mu m dual-stage polarization maintaining (PM) holmium-doped fiber amplifier (HDFA) operating in either continuous-wave (CW) or pulsed regime. The amplifier is pumped at 1860 nm, which offers a better efficiency than a 1940 nm pump. In CW regime, we measured more than 1W of output power at both 2051 nm and 2090 nm signal wavelengths. In pulsed mode, we tested the amplifier over a broad range of pulse widths (50-500 ns) and pulse repetition frequencies (PRFs) (50-1500 kHz). The PM HDFA delivered up to 200 W of peak power and 10 mu J of pulse energy with an excellent stability, while integrated inside a compact module.