Publications
58 results found
Ahmad H, Roslan NA, Zaini MKA, et al., 2023, Generation of multiwavelength bismuth-doped fiber laser based on all-fiber Lyot filter, Optical Fiber Technology, Vol: 81, ISSN: 1068-5200
A stable multiwavelength fiber laser was proposed and demonstrated using a bismuth-doped fiber together with an all-fiber Lyot filter. The proposed multiwavelength bismuth-doped fiber laser (BDFL) spectrum can generate up to 21 output channels between 1309.88 nm and 1313.69 nm by carefully adjusting two polarization controllers (PCs). The multiwavelength BDFL shows good stability over time with a signal-to-noise ratio (SNR) of 48.69 dB, contributing to the average power fluctuations of 0.6 dB and wavelength drift of less than 0.1 nm in the laser output. In addition, the multiwavelength BDFL exhibits a free spectral range (FSR) of about 0.192 nm and a frequency bandwidth of 33.45 GHz. The characteristics of the multiwavelength BDFL can be observed by varying the pump power of the pump source, lasing output at different lengths of polarization maintaining fiber (PMF), and the generation in multiwavelengths using additional single mode-fiber (SMF).
Hong Y, Taengnoi N, Bottrill KRH, et al., 2023, Experimental investigation of BDFA-based O-band direct-detection transmission using an optical recirculating loop., Pages: 10978-10990
We implemented a bismuth-doped fiber amplifier (BDFA) based optical recirculating loop to investigate the performance of amplified O-band transmission over appreciable distances. Both single-wavelength and wavelength-division multiplexed (WDM) transmission were studied, with a variety of direct-detection modulation formats. We report on (a) transmission over lengths of up to 550 km in a single-channel 50-Gb/s system operating at wavelengths ranging from 1325 nm to 1350 nm, and (b) rate-reach products up to 57.6 Tb/s-km (after accounting for the forward error correction redundancy) in a 3-channel system.
Wang Y, Wang S, Halder A, et al., 2023, (INVITED) Bi-doped optical fibers and fiber amplifiers, Optical Materials: X, Vol: 17
Bismuth (Bi)-doped aluminosilicate, phosphosilicate, germanosilicate and high (⩾50 mol%) germanosilicate fibers have shown luminescence around 1.15 μm, 1.3 μm, 1.45 μm and 1.7 μm, respectively. Bi-doped fibers have paved the way for developing optical amplifiers and fiber lasers in the wavelength region of 1150–1500 nm and 1600–1700 nm, where it can serve a wide range of applications in astronomy, imaging, medicine and advanced optical communications. However, spectroscopic study is required to understand the nature of near-infrared (NIR)-emitting Bi active centers (BACs) to improve the efficiency of Bi-doped fiber amplifiers and lasers. In this paper, we review the luminescence properties of Bi-doped glasses as well as Bi-doped fibers with aluminosilicate, phosphosilicate, and germanosilicate glass hosts. Absorption and emission cross-sections of Bi-doped phosphosilicate fibers are reported. In addition, we review the current state of the art of Bi-doped fiber amplifiers development in the second telecom window (O-band) and in the E-band and S-band for the next-generation high-capacity optical communications.
Taengnoi N, Bottrill KRH, Hong Y, et al., 2023, Demonstration of 100-km Long O-band WDM Amplified Coherent Transmission
O-band WDM 100-Gb/s/λ dual-polarization quadrature phase shift keying transmission is demonstrated over a 100-km link, with gain provided by bismuth-doped fiber amplifiers. Two different channel spacings are studied: 0.6nm and 10nm.
Wang Y, Halder A, Richardson DJ, et al., 2023, A highly temperature-insensitive Bi-doped fiber amplifier in the E+S-band with 20 dB flat gain from 1435-1475 nm
We report a bismuth-doped fiber amplifier operating in the E+S-band providing a 20.5±1dB flat gain with 5.5±2dB NF from 1435-1475nm for -10dBm input signal. The gain coefficient and temperature-dependent-gain coefficient are 0.065dB/mW and -0.005±0.001dB/, respectively.
Taengnoi N, Bottrill KRH, Hong Y, et al., 2023, Coherent O-band Transmission of 4×25 GBd DP-16QAM Channels Over a 50 km BDFA-Equipped Link
The first WDM O-band coherent transmission experiment in a BDFA-amplified link is reported. Four 25 GBd DP16QAM channels (4×200 Gb/s) are transmitted over 50 km of fiber, occupying a bandwidth of 4.7 THz.
Hong Y, Taengnoi N, Bottrill KRH, et al., 2022, Experimental demonstration of single-span 100-km O-band 4×50-Gb/s CWDM direct-detection transmission., Opt Express, Vol: 30, Pages: 32189-32203
We report on what is to the best of our knowledge the longest 50-Gb/s/λ O-band wavelength-division multiplexed (WDM) transmission. A pair of in-house built bismuth-doped fiber amplifiers (BDFAs) and the use of Kramers-Kronig detection-assisted single-sideband transmission are adopted to overcome the fiber loss and chromatic dispersion, respectively, in a reach-extended O-band coarse WDM (CWDM) system with a channel spacing of ∼10 nm. Through experiments on an amplified 4×50-Gb/s/λ direct-detection system based on booster and pre-amp BDFAs, we show the superior performance of single-sideband transmission in terms of both optical signal-to-noise ratio sensitivity and uniformity in performance amongst CWDM channels relative to double-sideband transmission after both 75-km and 100-km lengths of single-mode fiber. As a result, up to 100-km reach with comparable performance at all 50-Gb/s channels was achieved without the need for in-line optical amplification.
Thipparapu NK, Alam S, Wang Y, et al., 2022, Widely Tunable Actively Mode-Locked Bi-Doped Fiber Laser Operating in the O-Band, IEEE Photonics Technology Letters, Vol: 34, Pages: 711-714, ISSN: 1041-1135
Here, we propose an all-fiber actively mode-locked Bismuth (Bi)-doped fiber laser based on the use of an acousto-optic modulator. The mode-locked Bi-doped fiber laser produces 13ns pulses with a repetition rate of 1.683MHz at 1340nm. Higher harmonic mode-locking is achieved simply by changing the operating frequency of the acousto-optic modulator. The output power of the laser is 7mW and this is further amplified to 101mW using an external Bi-doped fiber amplifier. A peak power of 4.6W with a pulse energy of 60nJ is achieved after the master oscillator power amplifier. The stability of the laser is studied using an RF spectrum analyzer and an SNR of more than 60dB at the fundamental frequency of 1.683MHz was recorded. Furthermore, wavelength tuning of the Bi-doped fiber laser is explored and demonstrated from 1300 to 1370nm.
Ahmad H, Hidayah Abdul Kahar N, Yusoff N, et al., 2022, Passively Q-switched 1.3 μm bismuth doped-fiber laser based on transition metal dichalcogenides saturable absorbers, Optical Fiber Technology, Vol: 69, ISSN: 1068-5200
In this work, Q-switched fiber laser has been demonstrated in a bismuth-doped fiber laser (BDFL) system using tungsten ditelluride (WTe2) and tungsten disulfide (WS2) as saturable absorbers (SAs). The solution casting method was used to prepare both WTe2 and WS2 thin films SAs. At the threshold pump power, the generation of Q-switched pulse using WTe2 SA resulted in a pulse width of 10.4μ s and a repetition rate of 21.20 kHz. When the pump power was increased to maximum, the pulse width reduced to 8.0μ s, while the repetition rates increased to 22.46 kHz. Similarly, a Q-switched pulse was generated using WS2 SA, with an initial repetition rate of 18.86 kHz and a pulse width of 14.4μ s. The repetition rate of the pulses then increased to 19.53 kHz and pulse width reduced to 11.2 μs with the increasing pump power. The maximum pulse energy obtained for WTe2 and WS2 SAs was 13.93 nJ and 11.36 nJ, respectively, with a maximum average output power of 0.313 mW (WTe2) and 0.222 mW (WS2). This work uses the transition metal dichalcogenides (TMDs) materials to generate Q-switched pulses in BDFL operating at 1.3 µm region.
Wang Y, Rendón-Barraza C, MacDonald KF, et al., 2022, 3D Position Nanometrology of a Coronavirus-like Nanoparticle with Topologically Structured Light
Scattering of topologically structured light is highly sensitive to the position of a scattering object. We show that the position of a coronavirus-like 100 nm polystyrene sphere can be measured optically with deeply subwavelength accuracy.
Zhai Z, Halder A, Wang Y, et al., 2022, Temperature Dependent Characteristics of L-band EDFA Using Phosphorus- and High Aluminum- Co-doped Silica Fibers
We report a hybrid L-band amplifier employing phosphosilicate and high-aluminosilicate EDFs with 20.2±3.7dB gain and 4.2dB average NF from 1575-1615nm. The temperature-dependent-gain coefficient remains almost constant from 1585-1615nm over the temperature range -60 to +80°C.
Hong Y, Taengnoi N, Bottrill KRH, et al., 2022, 550-km Amplified Direct-Detection Transmission at 1.3μm
We report on transmission experiments in the O-band using a bismuth-doped fiber amplifier-based optical recirculating loop. Distances up to a record length of 550 km are demonstrated in a 50-Gb/s direct-detection system at the soft-decision forward error correction limit.
Hong Y, Taengnoi N, Bottrill KRH, et al., 2022, Demonstration of up to 480-km BDFA-based WDM Direct-detection Transmission in the O-band
We report on experiments of 3×50-Gb/s O-band WDM direct-detection transmission using a BDFA-based optical recirculating loop. Record-long transmission distances up to 480 km are achieved at the SD-FEC limit in experiments with two different channel spacings.
Wang Y, Rendón-Barraza C, MacDonald KF, et al., 2022, 3D Position Nanometrology of a Coronavirus-like Nanoparticle with Topologically Structured Light
Scattering of topologically structured light is highly sensitive to the position of a scattering object. We show that the position of a coronavirus-like 100 nm polystyrene sphere can be measured optically with deeply subwavelength accuracy.
Hong Y, Deligiannidis S, Taengnoi N, et al., 2022, ML-Assisted Equalization for 50-Gb/s/λ O-Band CWDM Transmission Over 100-km SMF, IEEE Journal of Selected Topics in Quantum Electronics, Vol: 28, ISSN: 1077-260X
We propose and demonstrate a bidirectional Vanilla recurrent neural network (Vanilla-RNN) based equalization scheme for O-band coarse wavelength division multiplexed (CWDM) transmission. Based on a 4 × 50-Gb/s intensity modulation and direct detection (IM/DD) system, we demonstrate the significantly better bit error rate (BER) performance of the Vanilla-RNN scheme over the conventional decision feedback equalizer (DFE) for both Nyquist on-off keying (OOK) and Nyquist 4-ary pulse amplitude modulation (PAM4) formats. It is shown that the Vanilla-RNN equalizer is capable of compensating for both linear and nonlinear impairments induced by the transceiver and the single-mode fiber (SMF). As a result, up to 100-km and 75-km SMF transmission can be achieved for OOK and PAM4 transmission, respectively. Furthermore, through the comparison with other equalization schemes, including the linear equalizer, 3rd-order Volterra equalizer, and Volterra+DFE, it is demonstrated that the Vanilla-RNN equalizer achieves the best BER performance. In the meantime, it also exhibits lower implementation complexity when compared to Volterra-based schemes. Our results show that the Vanilla-RNN scheme is a viable solution for realizing simple and effective equalization. This work serves as an exploration and offers useful insights for future implementations of reach-extended O-band CWDM IM/DD systems.
Zhai Z, Halder A, Wang Y, et al., 2022, Temperature Dependent Characteristics of L-band EDFA Using Phosphorus- and High Aluminum-Co-doped Silica Fibers
We report a hybrid L-band amplifier employing phosphosilicate and high-aluminosilicate EDFs with 20.2±3.7dB gain and 4.2dB average NF from 1575-1615nm. The temperature-dependent-gain coefficient remains almost constant from 1585-1615nm over the temperature range -60 to +80°C.
Ahmad H, Kamaruddin NH, Aidit SN, et al., 2021, Multi-wavelength Bismuth-doped fiber laser in 1.3 µm based on a compact two-mode fiber filter, Optics and Laser Technology, Vol: 144, ISSN: 0030-3992
In this work, a multi-wavelength Bismuth-doped fiber laser (MWLBDFL) operating in the 1.3 µm wavelength region is presented and experimentally demonstrated. The MWLBDFL leveraged on a 60 m Bismuth-doped fiber as an active gain medium, a compact two-mode fiber filter (TMFF) as a comb filter and a 2 km single-mode fiber section to induce four-wave mixing in the system. By optimising the polarization controller, the MWLBDFL generated 18 stable lasing output channels within 10 dB from the highest lasing line and a reasonably flat spectrum over a range of 11 nm. The stability of the MWLBDFL tested for a 150-minute duration showed a peak power fluctuation of less than 1 dB with a negligible wavelength drift. The extinction ratio of the TMFF was approximately 8.6 dB while the highest and lowest optical-signal-to-noise ratios (OSNRs) of the MWLBDFL were ~ 55 dB and ~ 50 dB, respectively. To the best of the author's knowledge, the proposed MWLBDFL demonstrates the highest number of output channels compared to other MWLs operating in the same wavelength region.
Ahmad H, Aidit SN, Samion MZ, et al., 2021, Tunable Dual-Wavelength Bismuth Fiber Laser with 37.8-GHz Frequency Spacing, Journal of Lightwave Technology, Vol: 39, Pages: 6617-6623, ISSN: 0733-8724
A tunable dual-wavelength Brillouin-bismuth fiber laser with a triple-Brillouin frequency spacing of ∼37.8 GHz was demonstrated by employing modular structures. The modular designs can be divided into two main cavities, whereby cavity 1 consisted of a 2-km single-mode fiber (SMF) and a loop mirror that was able to generate a single-spaced Brillouin shift, while cavity 2 comprised of 10-km dispersion compensating fiber (DCF) that was able to produce a double-spaced Brillouin shift. Based on this design, a stable dual-wavelength lasing was established with a low peak power fluctuation of 0.13 dB and 0.6 dB for the Brillouin pump (BP) and third Brillouin Stokes line (BS3), respectively. By varying the center wavelength of the Brillouin pump, the dual-wavelength laser can be tuned across a 40 nm span, ranging from 1300 nm to 1340 nm. The frequency spacing of the Brillouin-bismuth fiber laser can also be easily switched between ∼12.6 GHz, ∼25.2 GHz, and ∼37.8 GHz by utilizing these modular structures. The proposed dual-wavelength laser has a promising potential for application as a low phase noise source for microwave generation.
Wang Y, Thipparapu NK, Richardson DJ, et al., 2021, High Gain Bi-Doped Fiber Amplifier Operating in the E-band with a 3-dB Bandwidth of 40nm
We report a double-pass bismuth-doped fiber amplifier operating in the E-band providing 38dB gain with 6dB NF for -23dBm input signal at 1430nm. The amplifier 3-dB bandwidth and temperature-dependent-gain coefficient are 40nm and -0.006dB/, respectively.
Ahmad H, Azri MFM, Aidit SN, et al., 2021, 1.3 μm passively Q-Switched bismuth doped fiber laser using Nb<inf>2</inf>C saturable absorber, Optical Materials, Vol: 116, ISSN: 0925-3467
A tunable passively Q-switched fiber laser operating at 1.3 μm was demonstrated using bismuth-doped fiber (BDF) as the gain medium and using niobium carbide (Nb2C) as the saturable absorber (SA). The Nb2C was prepared using the solution casting method, and then fabricated into a film form for ease of integration into the laser cavity. Stable Q-switched pulses were observed as the pump power was increased from 820 to 1037 mW, generating pulses with increasing repetition rates from 10.1 kHz to 13.8 kHz and decreasing pulse widths from 17.54 to 7.58 μs. The all-fiber laser had a center wavelength at 1314 nm with a broad 3-dB bandwidth of 8.35 nm. The maximum output power and pulse energy of the Q-switched laser were 0.74 mW and 53.7 nJ, respectively. The laser was stable when tested for its long-term stability, where the peak frequency remained consistent at 13.8 kHz and the SNRs were maintained to be more than 60 dB throughout the entire test period. To the best of our knowledge, this is the first demonstration for a passively Q-switched fiber laser operating at 1.3 μm wavelength region using BDF as the gain medium.
Hong Y, Bottrill KRH, Wang Y, et al., 2021, O+E-band Transmission over 50-km SMF using A Broadband Bismuth Doped Fibre Amplifier
Ultra-wideband (UWB) transmission over single-mode fibres (SMFs) is an attractive route in optical transmission, since it allows the available low-loss bandwidth offered in conventional silica SMFs to be utilised more efficiently [1] - [3]. However, data transmission beyond a single span over wavelengths outside the erbium gain band remains challenging, primarily because of the lack of suitable optical amplifiers. Recently, the emergence of bismuth-doped fibre amplifiers (BDFAs) has shown considerable potential for amplified high-speed data communications outside the C+L-bands [4] - [8]. An exciting recent work has reported the development of a BDFA exhibiting a 115nm gain bandwidth, covering the range 1345-1460nm [8]. In this paper, we demonstrate the first data transmission experiment utilising this BDFA as a booster amplifier, and we study its performance across this entire gain band.
Thipparapu NK, Alam S, Wang Y, et al., 2021, Tunable Actively Mode-locked Bi-doped O-band Fibre Laser
Widely tunable pulsed fibre laser sources in the O-band (1260-1360nm) are of interest in a variety of fields including spectroscopy, optical communication, time-resolved measurements, and optical system diagnostics [1]. Furthermore, major constituents of biological tissues such as water, oxyhemoglobin, and melanin exhibit minimum optical loss windows in the 1300nm band pointing to applications in medicine [2]. Bi-doped phoshosilicate fibres (BPSFs) have recently been investigated as a promising medium to develop new wavelength lasers and amplifiers in the O-band [3]. They exhibit broad emission spectra which is an important characteristic for developing widely tunable pulsed laser sources [4]. However, to the best of our knowledge, there are no reports of tunable pulsed Bi-doped fibre lasers around 1300nm. Here, we demonstrate an actively tunable mode-locked Bi-doped fibre laser (ML-BDFL) operating in the wavelength region from 1300-1370nm.
Hong Y, Bottrill KRH, Taengnoi N, et al., 2021, Numerical and experimental study on the impact of chromatic dispersion on O-band direct-detection transmission., Appl Opt, Vol: 60, Pages: 4383-4390
The recent emergence of efficient O-band amplification technologies has enabled the consideration of O-band transmission beyond short reach. Despite the O-band being a low chromatic dispersion (CD) window, the impact of CD will become increasingly significant when extending the reach of direct-detection (DD) systems. In this work, we first numerically investigate the 3-dB bandwidth of single-mode fibers (SMF) and the CD-restricted transmission reach in intensity-modulation DD systems, confirming the significant difference between low- and high-dispersion O-band wavelengths. We then carry out experimental transmission studies over SMF for distances of up to 70 km at two different wavelengths, the low-dispersion 1320 nm and the more dispersive 1360 nm, enabled by the use of an O-band bismuth-doped fiber amplifier as a preamplifier at the receiver. We compare three 50-Gb/s optical DD formats, namely, Nyquist on-off keying (OOK), Nyquist 4-ary pulse amplitude modulation (PAM4) and Kramers-Kronig detection-assisted single-sideband quadrature phase shift keying (KK-QPSK) half-cycle subcarrier modulation. Our results show that at both wavelengths, OOK and QPSK exhibit better bit error rate performance than PAM4. When transmitting over 70-km of SMF at the less dispersive wavelength of 1320 nm, 50-Gb/s OOK modulation offers more than 1.5-dB optical power sensitivity improvement at the photodiode (PD) compared to 50-Gb/s QPSK. Conversely, at 1360 nm, the required optical power to the PD can be reduced by more than 3 dB by using QPSK instead of OOK.
Taengnoi N, Bottrill KRH, Hong Y, et al., 2021, Experimental characterization of an o-band bismuth-doped fiber amplifier., Opt Express, Vol: 29, Pages: 15345-15355
The recent emergence of bismuth-doped fiber amplifiers (BDFAs) offers the potential to transmit high-speed WDM signals over long distances in the O-band spectral region, thereby greatly enhancing the scope of systems utilizing these wavelengths. In this paper, we present a comprehensive experimental study on several basic characteristics of an O-band BDFA based on a phosphosilicate optical fiber, including the frequency-dependent noise figure, gain tilt (static and dynamic), transient response, and polarization dependent gain. We discuss our findings and their implications on the use of BDFA technology in high bit-rate multichannel systems.
Hong Y, Deligiannidis S, Taengnoi N, et al., 2021, Performance-enhanced Amplified O-band WDM Transmission using Machine Learning based Equalization
We investigate the performance of a machine learning-based equalization in an amplified 4×50-Gb/s O-band WDM system. The results show that the scheme offers significant receiver sensitivity improvements over decision-feedback equalization, especially at more dispersive wavelengths.
Ahmad H, Aidit SN, Ooi SI, et al., 2021, 1.3 µm dissipative soliton resonance generation in Bismuth doped fiber laser., Sci Rep, Vol: 11
In this work, a Figure-9 (F9) bismuth-doped fiber laser (BiDFL) operating in the dissipative soliton resonance (DSR) regime is presented. The 1338 nm laser used a BiDF as the active gain medium, while a nonlinear amplifying loop mirror (NALM) in an F9 configuration was employed to obtain high energy mode-locked pulses. The wave breaking-free rectangular pulse widened significantly in the time domain with the increase of the pump power while maintaining an almost constant peak power of 0.6 W. At the maximum pump power, the mode-locked laser delivered a rectangular-shaped pulse with a duration of 48 ns, repetition rate of 362 kHz and a radio-frequency signal-to-noise ratio of more than 60 dB. The maximum output power was recorded at around 11 mW with a corresponding pulse energy of 30 nJ. This is, to the best of the author's knowledge, the highest mode-locked pulse energy obtained at 1.3 μm as well as the demonstration of an NALM BiDFL in a F9 configuration.
Wang Y, Thipparapu NK, Richardson DJ, et al., 2021, Ultra-Broadband Bismuth-Doped Fiber Amplifier Covering a 115-nm Bandwidth in the O and e Bands, Journal of Lightwave Technology, Vol: 39, Pages: 795-800, ISSN: 0733-8724
In this article, we experimentally demonstrate an all-fiber optical amplifier using Bi-doped phosphosilicate fiber (BPSF) operating in both the O-band and the E-band, providing >20 dB gain from 1345 to 1460 nm for an input signal power of -23 dBm. A maximum gain of 31 dB with a noise figure (NF) of 4.8 dB was achieved at 1420 nm for -23 dBm input signal, whereas for an input signal power of -10 dBm it was 26 dB with a NF of 5.3 dB. The in-band OSNR of the proposed Bi-doped fiber amplifier (BDFA) was >22 dB from 1345 to 1460 nm for a -23 dBm input signal. The gain coefficient was found to be 0.04 dB/mW for a -23 dBm input signal. Also, the temperature dependent gain and NF performance of the BDFA within -40 to +60 °C were characterized. The temperature-dependent-gain (TDG) coefficient for a -23 dBm input signal was found to be -0.015 dB/°C at a signal wavelength of 1420 nm where the BDFA gain is maximum, while for an input signal power of -10 dBm it was -0.01 dB/°C at 1420 nm. The TDG coefficient of the proposed BDFA from 1350-1460 nm was in the range from -0.079 to -0.008 dB/°C. The BDFA gain and NF performance were also measured and compared using BPSFs with different unsaturable loss (UL) characteristics.
Hong Y, Deligiannidis S, Taengnoi N, et al., 2021, Performance-enhanced amplified o-band WDM transmission using machine learning based equalization
We investigate the performance of a machine learning-based equalization in an amplified 4×50-Gb/s O-band WDM system. The results show that the scheme offers significant receiver sensitivity improvements over decision-feedback equalization, especially at more dispersive wavelengths.
Hong Y, Bottrill KRH, Taengnoi N, et al., 2021, Amplified O-band direct-detection transmission using bismuth-doped fiber amplifiers, ISSN: 0277-786X
The recent emergence of bismuth-doped fiber amplifiers (BDFAs) enables the reach extension of high-speed O-band communication links. In this work, our recent efforts on amplified O-band direct-detection (DD) transmission using BDFAs are reviewed. We first present the performance of a four-channel O-band coarse wavelength-division multiplexed (CWDM) transmission over 50-km length of single-mode fiber (SMF), showing that the chromatic dispersion (CD) which has long been neglected in O-band transmission, will degrade the transmission performance of dispersive O-band channels. In this context, we quantify the relative benefits of different DD formats at 50 Gb/s over up to 70-km length of SMF in a BDFA pre-amplified O-band system. The considered formats include Nyquist on-off keying (OOK), Nyquist 4-ary pulse amplitude modulation (PAM4), and Kramers-Kronig (KK) detection assisted subcarrier modulation using quadrature phase-shift keying (QPSK), and they are evaluated over both the low CD 1320-nm wavelength and the more dispersive 1360-nm wavelength. It is demonstrated that OOK exhibits the best receiver sensitivity over all distances up to 70 km at the 1320-nm channel, whereas KK-QPSK achieves the optimal transmission performance at the 1360-nm wavelength when the reach is extended beyond 50 km. We consider that our results provide useful insights into possible future implementations of longer-reach O-band WDM systems.
Wang Y, Thipparapu NK, Richardson DJ, et al., 2021, Bi-doped fiber amplifiers for ultra-wideband optical communication systems, ISSN: 1099-4742
Bismuth (Bi)-doped fibers provide great potential for developing optical amplifiers in the low-loss transmission window, 1250-1650nm, of silica fibers. In this paper, we review recent progress of Bi-doped fiber amplifiers (BDFAs) covering 1345-1460nm spectral region. We also present the BDFA performance at different ambient temperatures.
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