Broadband ASE Research Articles

Broadband ASE source-enabled self-homodyne DA-RoF fronthaul using cascaded SOAs and a multicore fiber.

Broadband amplified spontaneous emission (ASE) light sources are recognized for their cost-effective generation. However, their inherent high-intensity noise and the stringent requirement for time delay matching limits their widespread application in coherent optical telecommunication. Here we propose a broadband ASE source-enabled digital-analog radio-over-fiber (DA-RoF) mobile fronthaul architecture, leveraging semiconductor optical amplifiers (SOAs) and multicore fiber in tandem. Our proposed system uses SOAs to suppress the intensity noise of the ASE carrier and transmits the DA-RoF signal alongside an unmodulated carrier through distinct cores of an 8-core, 1-km fiber. This setup significantly enhances the signal-to-noise ratio (SNR) by 19.4 dB, boosts capacity, and enables self-homodyne detection at the receiver end. We achieve an aggregated bandwidth of 35 GHz (7 cores × 5 GHz), supporting a 2.05-Tb/s CPRI-equivalent data rate with 1024-ary quadrature-amplitude-modulated (1024-QAM) signals. Additionally, we analyze the impact of chromatic dispersion on signal-to-noise ratio for broadband source coherent detection systems. This innovative scheme offers a pragmatic solution for integrating low-cost broadband sources into cost-sensitive fronthaul systems, providing both high capacity and fidelity in massive deployment scenarios.

2 μm Watt-level Fiber Amplifiers, Lasers, and ASE Sources Pumped by Broadband ASE Pumps

2 μm Watt-level Fiber Amplifiers, Lasers, and ASE Sources Pumped by Broadband ASE Pumps

Flat Millimeter-Wave Noise Generation by Optically Mixing Multiple Wavelength-Sliced ASE Lights

We propose a photonic method for flat spectrum millimeter-wave (mm-wave) noise generation. Specifically, the flat spectrum mm-wave noise is obtained by slicing the broadband ASE optical spectrum into multiple Gaussian-shaped spectra with different central wavelengths, then beating in a wideband photomixer. Our simulation demonstrates that flat spectrum mm-wave noise can be generated in a very large range of frequency of F-band (90-140 GHz) and G-band (140-220 GHz). For the quantitative comparison of the quality of generated mm-wave noise, we define the relative flatness ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\eta$ </tex-math></inline-formula> ) as the ratio of the generated noise power fluctuation to its average power within a certain frequency range. Our experimental results show that the relative flatness of the generated mm-wave noise is as low as 0.46 (@35 ± 15 GHz).

Fiber Bragg Grating Sensor Interrogation Using Tunable Erbium-Doped Fiber Ring Laser Source

Fiber Bragg gratings (FBG) are ideal sensors for temperature, strain or vibration sensing applications with their advantages over conventional electronics sensor systems. In this paper, two different FBG sensor interrogation schemes based on broadband ASE source and tunable EDFRL source are demonstrated and compared. With both interrogator configurations, the response of the FBG sensor to temperature change is found to be linear and the sensitivities are measured as 11 pm/°C and 10.5 pm/°C, respectively. The experimental results have revealed that the optical power reflected from the FBG sensor is almost 20 dB higher with tunable EDFRL source than broadband ASE source. Thus, an interrogation method with tunable EDFRL can be suitable for remote, quasi-distributed sensor applications requiring high output power and OSNR.

High contrast reflectance imaging at 1950 nm for the assessment of lesion activity on extracted teeth.

Changes in the reflectivity of lesions on the proximal surfaces of extracted human teeth were measured at SWIR wavelengths from 1300-2000 nm as they were dried with air to assess lesion activity. An extended range tungsten-halogen lamp with bandpass filters of varying wavelength (bandwidth) 1300 nm (90), 1460 nm (85), 1535 nm (80), and 1675 nm (90) along with a broadband ASE source centered near the peak of the water-absorption band at 1950-nm were used as light sources and an extended range InGaAs camera (1000-2340 nm) was used to acquire reflected light images as the samples were dried with air. MicroCT images were used as a gold standard for comparison. SWIR light at 1950 nm yields extremely high contrast of demineralization and appears to be the optimum wavelength for the assessment of lesion activity on tooth coronal surfaces.

Broadband visible-to-NIR ASE from Bismuth doped optical fibers: a window towards lasing

We report broadband ASE within 650–825 nm, peaking at 655, 680, 715 nm, from Bismuth (Bi) doped optical fibers (BDFs) under 533 nm core-pumping excitation technique; 715 nm peak was prominent among others. Fiber preforms were fabricated through MCVD process associated with solution doping technique using Bi-,Yttrium/Lithium co-doped phosphosilicate, germanosilicate glasses (BYPS/BYGS/BLGS) as core materials. Optimum fiber lengths providing maximum ASE were 15 cm for BYPS and 35 cm for BYGS fibers. Possible issues behind strong ASE without any lasing were demonstrated using modal analysis of BDFs at 533 and 715 nm. This study is a step towards developing visible-to-NIR laser using BDFs of such types.

Detonation velocity measurements with uniform fibre Bragg gratings.

In this paper we demonstrate a simple and new fibre optic technique for measuring detonation velocities using uniform fibre Bragg gratings. We compare this new system with chirped fibre Bragg grating diagnostics and show how coherent source illumination can yield spatial uncertainties below ±10 μm - a percentage error that is an order of magnitude lower than the broadband ASE methods we have tested.

The Transformer Winding Temperature Monitoring System Based on Fiber Bragg Grating

Abstract High temperature is one of the important reasons causing the fire in power system. Therefore, the early warning could be told by monitoring the temperature and effective measures could be taken. The corresponding accidents will be reduced. The traditional transformer winding temperature monitoring methods are electrical signal measurement and infrared measurement. Such electrical signal sensors are vulnerable to the interference of electromagnetic field, so the result of measurement is bad. Multiplexing optical path is unable to be realized by fluorescence thermometry. The optical fiber Bragg grating technology is used on temperature monitoring of transformer winding in this paper. The transformer winding temperature monitoring system based on optical fiber Bragg grating includes three parts: Temperature monitoring program based on the LabVIEW programming language, a fiber Bragg grating wavelength demodulation system and FBG temperature sensor. When the temperature of the transformer windings changes, the central wavelength of the fiber Bragg grating changes accordingly. Broadband ASE light source emits light, which is transmitted from the optical circulator into the fiber Bragg grating. The reflected light gets into the wavelength demodulation module again through the optical circulator. Wavelength demodulation module could transmit the center wavelength of the spectral reflectance information, peak power information to the computer. The computer analyzes, processes the information and displays the data with XY graph by calling the LabVIEW program. The program can get center wavelength values at the same time then get temperature by fitting function and display temperature on the front panel of the program. The fitting line of linearity between center wavelength of optical fiber Bragg grating sensor and temperature is above 0.95. The function reveals a good linearity which fitting the wavelength changes of the optical fiber Bragg grating during this temperature range. The experimental results show that the system has high accurate measurement which meeting high precision requirements of transformer winding temperature.

Optimal design of 32 channels spectrum slicing WDM for optical fiber access network system

In this article, the spectrum sliced dense wavelength division multiplexed passive optical network (SS-DWDM–PON) has been investigated as a power efficient and cost effective solution for optical access networks. In this work an AWG demultiplexer is used to operate as slicing system. The high speed SS-DWDM system has been realized and investigated for 32 channels with data rate up to 3Gb/s using broadband ASE source (LED). The 3Gb/s signals both non-return-to-zero (NRZ) and return-to-zero (RZ) were demonstrated in 40km optical fiber link with BER<10−12. The results obtained here demonstrate that SS-DWDM is well suited for Fiber-to-the-Home (FTTH) network.

Silicon-based optoelectronic integrated circuit for label-free bio/chemical sensor

We demonstrate a silicon-based optoelectronic integrated circuit (OEIC) for label-free bio/chemical sensing application. Such on-chip OEIC sensor system consists of optical grating couplers for vertical light coupling into silicon waveguides, a thermal-tunable microring as a tunable filter, an exposed microring as an optical label-free sensor, and a Ge photodetector for a direct electrical readout. Different from the conventional wavelength-scanning method, we adopt low-cost broadband ASE light source, together with the on-chip tunable filter to generate sliced light source. The effective refractive index change of the sensing microring induced by the sensing target is traced by scanning the supplied electrical power applied onto the tracing microring, and the detected electrical signal is read out by the Ge photodetector. For bulk refractive index sensing, we demonstrate using such OEIC sensing system with a sensitivity of ~15 mW/RIU and a detection limit of 3.9 μ-RIU, while for surface sensing of biotin-streptavidin, we obtain a surface mass sensitivity of S(m) = ~192 µW/ng·mm(-2) and a surface detection limit of 0.3 pg/mm(2). The presented OEIC sensing system is suitable for point-of-care applications.

Active optical fibres for application in laser and broadband ASE sources

Abstract The article brings into focus the present state of technology employing active fibres doped with rare earth (RE) ions for applications requiring power supply of several dozen watts and broadband ASE sources. Current trends in development of glasses and in construction of active fibres used in fibre sources of radiation within VIS-NIR range are presented. Technological constraints in the doping of fibre core glasses are discussed, with particular consideration of optimal RE concentration for technical applications. Characteristics of glasses are offered, and the glasses are used for manufacturing optical fibres with luminescence within the visible as well as near- and mid-infrared ranges. Also, requirements and luminescence properties concerning glasses co-doped with e.g. Nd3+/Yb3+,Tm3+/Ho3+ and Yb3+/Tb3+ are discussed. Results of research on the impact of technological parameters of glass matrices on luminescence properties of core glasses and optical fibres are quoted. For the doped glasses of which luminescence in a wide spectral range is desired, conditions for their processing into optical fibre systems are mentioned. Additionally, the impact of phonon energy in the glass on producing emission in a specified spectral range is analyzed. Furthermore, the article presents directions of technological studies to solve problems persisting in the phase of glass matrix design, as well as in determining the influence of fibre drawing process on the luminescence properties of core glasses and optical fibres, confirming the differences in luminescence stemming from the drawing process. Finally, some original designs of core glasses and active multicore fibre systems devised for construction of fibre radiation sources are presented.

An airborne acoustic fiber sensor using fiber Bragg grating with wavelength division coupler demodulating method

In this paper, we report an airborne acoustic fiber sensor. It consists of a broadband ASE light source, a circulator, a fiber Bragg grating (FBG) with a central reflecting wavelength of 1550nm, a round nickel membrane with a diameter of 9mm and a thickness of 3μm, and a wavelength division multiplexed (WDM) coupler demodulating module. The fiber Bragg grating is bonded to the nickel membrane along the central line with epoxy. The principles of the fiber sensor are described as follows: the sound wave causes the membrane to vibrate and the FBG bonded to the membrane to be bent. The shifts of the central reflecting wavelength caused by FBG bending are modulated by sound waves. The shifts are demodulated by a WDM system with an acoustic signal processing unit. The fabricated fiber sensor shows some advantages, such as water-proof character (about 2m deep under water), easy extending to arrays and easy fabrication procedures. It has widely potential applications in acoustic detection fields.

Broadcast/multicast transmission of video signal in a WDM-PON using a low-cost injection-locked F-P LD with broadband ASE

A broadcast/multicast transmission method in a WDM-PON system using a low-cost Fabry-Perot laser diode with broadband ASE injection is proposed and experimentally demonstrated in this paper. Because of its low front-facet reflectivity (∼0.1%), the F-P LD exhibits a broadband lasing spectrum and reduced mode-partition noise. To demonstrate its performance, the bit error rate and packet loss rate were measured. The proposed optical source provides a cost-effective WDM-PON architecture for a broadcast/multicast service accommodating more than 32×622MBps. For the transmission of MPEG-2 TS packets, zero packet loss could be obtained at an optical power of -32dBm.

Broadband ASE light source for 1800 nm wavelength region

The first ASE light source with a flat and broadband ASE spectrum in the 1800 nm wavelength region has been developed by combining a Tm3+-Tb3+-doped fibre and a Tm3+-doped fibre. The achieved bandwidth where the ASE intensity exceeded −20 dBm/nm was 162 nm (from 1690 to 1852 nm).

Compromised extinction and signal-to-noise ratios of weak-resonant-cavity laser diode transmitter injected by channelized and amplitude squeezed spontaneous-emission

By using a 200GHz AWG channelized ASE source in connection with a saturable semiconductor optical amplifier (SOA) based noise blocker as the injecting source at the remote node in front of the local optical network units (ONUs), we demonstrate the spectrum-sliced ASE transmitter with greatly suppressed intensity noise performance in WDM-PON network. Such channelized SOA filtering technique effectively reduces the relative intensity noise of the ASE source by at least 4.5 dB. The low-noise WRC-FPLD transmitter improves its extinction-ratio (ER) from 8.9 to 9.6 dB and signal-to-noise ratio (SNR) from 5.9 to 6.3 dB. In comparison with broad-band ASE injection-locked WRC-FPLD transmitter at same power, there is an improvement on receiving power penalty (DeltaP(Receiver)) by 2 dB at BER 10(-9) in back-to-back case, and the receiving power of BER 10(-9) can achieve -24 dBm even after 25km fiber transmission. With additional AWG filtering, the intraband crosstalk effect between the upstream transmitted data and the reflected ASE signal is significantly reduced by 6.3dB. The compromised effects of ER and SNR on BER performance are also elucidated via the modified SNR model for the WRC-FPLD under ASE injection induced gain-saturation condition. The DeltaP(Receiver)/DeltaSNR of 8.89 at same ER condition is more pronounced than the DeltaP(Receiver)/DeltaER of 3.17 obtained under same SNR condition, indicating that the SNR plays a more important role than the ER on enhancing the BER performance.

CO2 monitoring and detection using an integrating sphere as a multipass absorption cell

This paper describes a multipass absorption sensor based on an integrating sphere. The sphere has an internal coating which is highly reflective (over 95%) in the near infrared region and this allows for the detection of CO2 at two regions in the spectrum: 2 µm and 1.57 µm. CO2 was detected around the 2 µm region using a light emitting diode as the emitter and a photodiode as the detector, while detection at the 1.57 µm region took place using a broadband ASE source as the emitter and a miniature spectrometer as a detector. A 2 in diameter (50.8 mm) integrating sphere was used as an absorption gas cell. This paper reports the generation of effective optical path lengths of 114 cm at the 1.57 µm region and 40 cm at the 2 µm region. Experimental results demonstrating the detection of CO2 using a 2 in diameter integrating sphere are presented and simulation results based on larger integrating spheres are also reported. Further simulations conducted in the mid-infrared region suggest the possibility of detecting trace levels of CO2 (less than 200 ppm) using a 2 in diameter integrating sphere.

Raman amplification-based WDM-PON architecture with centralized Raman pump-driven, spectrum-sliced erbium ASE and polarization-insensitive EAMs

We propose a novel wavelength division multiplexed (WDM) passive optical network (PON) architecture based on the distributed Raman amplification and pump recycling techniques, which features fully bidirectional transmission, relaxed signal power margin, and active light source-free, colorless subscriber units. The reuse of non-negligible residual Raman pump power as a pump for an erbium fiber-based upstream broadband ASE source allows for fully-centralized control of light sources at optical network units (ONUs), while distributed Raman amplification over a transmission link enables us to obtain lossless low power signal transmission. Furthermore, low-cost and colorless ONUs can be realized by use of the Raman pump-recycled erbium ASE and polarization-insensitive electroabsorption modulators. Error-free upstream transmission over a 50 km fiber link is successfully achieved at a data rate of 622 Mbit/s.

Low-cost WDM passive optical network with directly-modulated self-seeding reflective SOA

A novel scheme facilitating self-seeding reflective semiconductor optical amplifiers as colourless upstream transmitters in a low-cost WDM-PON solution, eliminating centralised broadband sources and active temperature control, is experimentally demonstrated. A single passive broadband filter is used to reflect broadband ASE light from all transmitters for self-seeding. Direct modulation of the incoherent upstream channels shows no significant penalty after 21 km of transmission.

100 mW spectrally-uniform broadband ASE source forspectrum-slicedWDM systems

A > 100mW source of broadband ASE with exceptionally flat spectral density and 22nm bandwidth is presented. The source is ideally suited for spectrum-sliced WDM systems. Data transmission at 622Mbit/s using a spectraily-sliced channel tuned over a 15nm range is demonstrated.