A continuously tunable, coherence free microwave photonic filter is proposed and experimentally demonstrated. The
filter is based on a high-birefringence linearly chirped fibre Bragg grating (Hi-Bi LCFBG) as the tuning component. The
filter response tunability is realized through changing the differential group delay of the Hi-Bi LCFBG by applying
gradient tension or adjusting the operating wavelength. Free spectral range tuning by 1.11 GHz with about 40 dB notch
rejection is achieved.
For measurements of the Mueller matrix and other polarization effect matrices in a birefringent optical system, such as an optical fiber, we demonstrate by theoretical analysis and simulation that two input polarization states that are mutually orthogonal in Stokes space statistically have the maximum probability to achieve the optimum measurement accuracy. But in a single test, evident deviation from perpendicularity can be observed for achieving the minimum measurement error. For measurements of both polarization effect matrices and polarization effect vectors, we find that all measurement errors have a bathtub-shaped relationship with the angle between two input polarization states in the range from 0 to 180 deg. This means a limited offset from perpendicularity will only slightly and statistically increase the measurement error in a single test.
Microwave signals distributed over optical fibre are of great interest for many applications. There are many
advantages of all-optical microwave filters for the direct processing of microwave signals in the optical domain, such as,
large time-bandwidth products, insensitivity to electromagnetic interference, low loss, and lightweight. A number of low
pass photonic microwave filters have been reported, where it is required to achieve optically incoherent summing of two
light beams. To overcome the optical coherence problem, either a laser array is used, or the coherence length of the light
source is kept smaller than the minimum delay time of the filter. Incoherent summing in bandpass filter has also been
achieved; however, they require very long length of Hi-Bi fibre.
We propose here all-optical low pass and bandpass microwave photonic filters configurations, together with their
application in a 20 km radio-over-fibre (RoF) link. The key problem when using a narrow linewidth source is the
coherent operation because of the narrow laser source. High differential group delay (DGD) will be induced by Hi-Bi
linearly chirped fibre Bragg grating (LCFBG), the optical interference is avoided because the two orthogonal state of
polarizations (SOPs). Meanwhile, the positive or negative chromatic dispersion (CD) will also be provided by the
chirped Hi-Bi LCFBG. The bandpass resonance is eliminated by the use of phase modulation. The CD value also can be
compensated or increased by the chirped LCFBG in the RoF link for both low pass and bandpass filters. Measured
results agree well with the theoretical results.
The spatially and spectrally resolved polarization mode dispersion (PMD) measurement technique is proposed to
measure PMD values of every fiber sections in an optical fiber link in the wavelength range interested. This technique is
validated by comparing the results of reflectometric and forward measurements.
Distributed sensors, based on Brillouin effect in the optical fiber, provide an excellent method for measuring temperature
and strain over long distances. There are two types of such sensors. The first type is based on spontaneous Brillouin
scattering, and is called Brillouin optical time domain reflectometer (BOTDR). It measures the Brillouin frequency shift
or Brillouin power or Brillouin gain bandwidth to get the temperature and strain information. The second type of sensor
is based on stimulated Brillouin amplification. It is called Brillouin optical time domain analyzer(BOTDA). Normally, it
uses one laser at each fiber ends, one as pump and the other as a probe light. The probe light will experience Brillouin
amplification. Through the analysis of Brillouin gain spectrum (BGS), we can get the temperature and strain information.
Both the two types of sensors are attracting attention all over the world, and temperature resolution of less than 1 degree
and strain resolution up to 5 με was reported. The fiber distances of up to 150km was presented while other papers
reported a spatial resolution of the order of 1cm with frequency domain techniques or correlation techniques. We
proposed and analyzed our design, it is an improvement of BOTDA with a single end laser, which make it easy to
implement in field. Through simulations, optimized launch power has been found for a certain design.
It is essential to extend the optical buffer depth to meet the burst-mode packet requirement. In this paper, we
propose to incorporate the Mach-Zehnder interferometer (MZI) into our successful SOA-based dual loop optical
buffer (DLOB) configuration. The maximum packet length for the DLOB storage is evaluated theoretically, and the
fiber loop utilization can be greatly enhanced with our modified configuration. Then we have successfully
demonstrated the 2.5 Gbps variable-length packet loadable function with the MZI-DLOB configuration. The
waveform of variable-length packet is little degraded after optical storage. Meanwhile an effective polarization
stable method is also experimentally implemented to reduce the instability of MZI-DLOB. All the obtained results
confirm the feasibility of our configuration to apply in variable-length optical packet switching.
A virtual Mueller matrix method is proposed to measure the first- and second-order polarization mode dispersion (PMD) vectors in optical fibers. This method not only can use a large frequency step to attain low-noise PMD vector data, but also does not require knowledge of the input polarization states. Our measurement method has a simpler setup and is more accurate than the traditional Mueller matrix method.
In this paper, we propose and demonstrate a novel room temperature multiwavelength erbium-doped fiber laser (EDFL) scheme with the wavelength spacing less than homogeneous broadening linewidth based on the inter-channel four-wave mixing (FWM). A stable CW MW-EDFL is firstly implemented based on a length of high nonlinear photonic crystal fiber (HNL-PCF) and sampled-fiber Bragg grating (SFBG). We further extend the idea of FWM induced self-stable operation of MW-EDFL to the multiwavelength mode-locking fiber ring laser to generate ultra-short, ultra-fast, multiwavelength and synchronized pulse sources. 2 and 4 wavelengths anchored on ITU-T standards with 100 GHz channel spacing are successfully mode-locked at 10-GHz simultaneously, without gain competition.
In this paper, we demonstrate a novel stabilization scheme of actively harmonically mode-locked Erbium-doped fiber lasers (ML-EDFLs) by using highly nonlinear fibers in the cavity. 2 and 4 wavelengths anchored on ITU-T standards with 100 GHz channel spacing are successfully generated without gain competition. The amplitude fluctuation and timing jitter are measured to be less than 1% and 100fs, respectively.
Polarization mode dispersion vectors measurement methods are integrated into a unitive theoretical model. A clear comparison among these methods is conducted to clarify their advantages and disadvantages. Experimental results on optical fiber systems with and without PDL/G are implemented to compare these methods.
Several measurement methods for polarization dependent transmission in an optical fiber link are compared. The
relationship between these methods is discussed. Guidelines for choosing a particular method are provided based on
accuracy, speed, and system characteristics.
We experimentally demonstrate a temperature-stable multiwavelength erbium-doped fiber laser source using a high-birefringent photonic crystal fiber (HiBi-PCF) as the birefringent component of the Sagnac loop filter within the laser cavity. Three different high-birefringence (Hi-Bi) fibers are used in the loop filter to compare the temperature stability of the fiber laser systems: polarization-maintaining erbium-doped fiber (PM-EDF), panda Hi-Bi fiber, and HiBi-PCF. Because of the high birefringence and low temperature sensitivity of the HiBi-PCF, fiber length in the loop is greatly reduced and the temperature stability of the system is dramatically enhanced.
We propose a novel, continuously tunable, photonic microwave notch filter configuration that uses, for the first time, single-sideband (SSB) modulated optical signals together with a linearly chirped fiber grating in a Sagnac loop. Measured results are presented to show a large notch rejection and an easily tunable free spectral range (FSR) by tuning the chirped fiber Bragg grating (FBG). The configuration enables doubling of time delay in the Sagnac loop. Use of SSB offers the potential to overcome chromatic dispersion.
It is essential to increase or decrease storage time of a Dual Loop Optical Buffer (DLOB) by properly selecting fiber loop length. We experimentally investigate the performance constraint of DLOB owing to the Four-wave mixing (FWM). Our results show that some parameters, such as the control signal wavelength, length of fibre loop, types of
fibre have strong impacts on the performance of DLOB. The storage time can be increased by power compensation, but the signal become degraded after several loops due to FWM. To decrease the buffer time, the power of the control signal is increased and high-nonlinear fibre is selected to shorten the fibre loop, but the FWM can not be eliminated and has a critical impact on the performance of DLOB.
We present how to obtain the forward linear birefringence and the angle increment of birefringent axis distributions from the round-trip local birefringence vector by using P-OTDR technique. Further we can use these data to calculate the DGD distribution in two ways, one is to show the DGD for every fiber sections and the other is to show the DGD evolution along the fiber. The experimental results are in good agreement with the theoretical results and the result measured using JME method.
We investigated the first- and second-order round-trip local birefringence vectors (which are the round-trip local birefringence vector and its derivative, respectively) obtained by using P-OTDR technique in optical fibers. We found the twist-induced circular birefringence can be expressed with the modulus of the two vectors and the derivative of the modulus of the first-order vector. Based on this theory, twist-induced circular birefringence distribution along the fiber can be measured. We also proposed a simple way to measure the round-trip local birefringence vectors
P-OTDR is the effective method for measuring distribution of PMD in a single-mode fiber, this paper analysis the effect of coherence of light source on measurement, that, when the width of input pulse is short enough, this effect can be neglected. But, when we estimate the effect of width of pulse on the measurement results, the coherence of light source must be considered.
Investigating the Miller matrix in optical fiber, this paper derives, for the first time, the expression ofthe vector of PMD (polarization mode dispersion), expression of the Stocks vector of Principal State of Polarization (PSP), and expression of the high-order vector of PMD, which are determined by the parameters of fiber. Then the relationship between vectors of local and whole PMD and the principle of PMD compensation are also discussed. Introducing the vector of compensating PMD and calculating the vector of compensating PMD of a piece of uniform non-circle birefringence wave-guide, we prove theoretically that it is impossible to compensate PMD by use of a piece of uniform non-circle birefringence wave-guide, such as one piece of polarization maintaining fiber. A novel PMD compensation scheme based on PMD vector and adjustment algorithm are given. All conclusions are very helpful to PMD compensation.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.