Papers by Faramarz E. Seraji
Growing demands of the internet users is one of the reasons that lead using dense wavelength divi... more Growing demands of the internet users is one of the reasons that lead using dense wavelength division multiplexing (WDM) networks to transmit optical data. This modulation technique has the capability of transmitting several wavelengths through a single optical fiber. In this study, we have simulated a 160 Gb/s DWDM network with transmission power of 0 dBm, using NRZ encoding technique through a 32-chanels optical transmitter over a distance of 1000 km. To this aim, we have assumed a link of 10 spans with a length of 100 km fiber for each span. An EDFA and a DCF have been used for amplifying signals and compensating pulse dispersion, respectively. All simulations have been run by using Optisystem software. The quality of the network was estimated by using the eye-diagrams of the received signals. The maximum quality factor of 20.7 and minimum bit error rate of 7.6×10-95 are obtained at wavelength of 1552.5 nm. The eye-diagrams showed an ideal quality for the received signals. More research works are needed to evaluate the parameters that affect on the quality of the DWDM optical systems.
Bookmarks Related papers MentionsView impact
In this evaluation, we have compared two popular return to zero (RZ) and non-return to zero (NRZ)... more In this evaluation, we have compared two popular return to zero (RZ) and non-return to zero (NRZ) modulation formats in a 100-km and 400-km single-channel and wavelength division multiplexing (WDM) optical networks for bit rate of 10-Gb/s and 160-Gb/s, respectively, by using Optisystem software. The results showed the better performance of the RZ technique in tolerating the non-linear effects and noisy environments. It's shown that NRZ technique is a good option for single-channel networks and long-haul WDM links. The obtained evaluation results show that the RZ technique is a better choice for short-distance WDM links.
Bookmarks Related papers MentionsView impact
This paper presents a simple analysis on the nonlinear behavior of a practical APD receiver circu... more This paper presents a simple analysis on the nonlinear behavior of a practical APD receiver circuitry, by considering a silicon APD photodetector as an optical receiver. The analysis presents the effects of received input power by the photodetector and the load resistance at the receiving end on the total harmonic distortion (THD), consisting of second and third harmonics. The behavior of the THD is formulated and graphically illustrated in terms of the input power and load resistance. Typically, for a given circuit, the second HD was found to be -71 dB, for load resistance of RL =100 Ω and optical input power of Pa =1μW. If a high impedance preamplifier is used with RL =10 kΩ, the second HD will worsen to a value of -11 dB for Pa =10 μW. The analysis is given in an easy-to-understand manner that can be readily
applied to a practical system and would be useful when dealing with analog optical fiber communication systems and optical
fiber sensing systems.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Characterization of doped optical fibers (DOFs) is an essential primary stage for design of DOF-b... more Characterization of doped optical fibers (DOFs) is an essential primary stage for design of DOF-based devices. This paper presents design of novel measurement techniques to determine DOFs parameters using mono-beam propagation in a low-loss medium by generating pseudo parameters for the DOFs. The designed techniques are able to characterize simultaneously the absorption, emission cross-sections (ACS and ECS), and dopant concentration of DOFs. In both the proposed techniques, we assume pseudo parameters for the DOFs instead of their actual values and show that the choice of these pseudo parameters values for design of DOF-based devices, such as erbium-doped fiber amplifier (EDFA), are appropriate and the resulting error is quite negligible when compared with the actual parameters values.Utilization of pseudo ACS and ECS values in design procedure of EDFAs does not require the measurement of background loss coefficient (BLC) and makes the rate equation of the DOFs simple. It is shown that by using the pseudo parameters values obtained by the proposed techniques, the error in the gain of a designed EDFA with a BLC of about 1 dB/km, are about 0.08 dB. It is further indicated that the same scenario holds good for BLC lower than 5 dB/m and higher than 12 dB/m. The proposed characterization techniques have simple procedures and are low cost that can have an advantageous use in manufacturing of the DOFs.
Bookmarks Related papers MentionsView impact
This paper presents an analysis of the effect of temperature rise and hydrostatic pressure on mic... more This paper presents an analysis of the effect of temperature rise and hydrostatic pressure on microbending loss, refractive index change, and stress components of a double-coated optical fiber by considering coating material parameters such as Young’s modulus and the Poisson ratio.
It is shown that, when temperature rises, the microbending loss and refractive index changes would decrease with increase of thickness of primary coating layer and will increase after passing through a minima. Increase of thickness of secondary coating layer causes the microbending loss and refractive
index changes to decrease.
We have shown that the temperature rise affecting the fiber makes the microbending loss and refractive index decrease, linearly. At a particular temperature, the microbending loss takes negative values, due to tensile pressure applied on the fiber.
The increase of Young’s modulus and the Poisson ratio of primary coating would lower the microbending loss and refractive index change whereas in the secondary coating layer, the condition reverses.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
The dispersion of optical pulses propagating in high speed WDM optical transmission systems is al... more The dispersion of optical pulses propagating in high speed WDM optical transmission systems is almost unavoidable. For a reasonable compensation of the dispersion, use of dispersion compensating fibers (DCF) is one of accepted approaches being practiced in past two decades. Due to their peculiar refractive index profile, the DCFs have relatively high attenuation when inserted as a device in a network. In this paper, by using the Optifiber software, four varieties of single-mode fibers of high compensating capabilities with a low bending losses are designed, optimized, and then compared with a fabricated sample developed by Fujikura Co. In an optimized design case, a negative dispersion of -517 ps/nm.km with a bending loss of 3.3 dB/km at bending radius of 20 mm is obtained.
Bookmarks Related papers MentionsView impact
Analysis of losses at splice joints of dissimilar single-mode fibers (SMF), with three types of p... more Analysis of losses at splice joints of dissimilar single-mode fibers (SMF), with three types of photonic crystal fibers (PCFs) are presented, using full-vectorial effective index methods and scalar effective index method. The effects of air-hole diameter (d) , air-hole spacing (Λ) , the air-filling factor d / Λ , dopant concentration in the core of PCFs on power coupling ratio and coupling losses at splice joints are analytically investigated. The results of the analysis may be used by network designers to predict over all splice joints losses when employing PCF-based devices in the optical networks.
Bookmarks Related papers MentionsView impact
Loss and dispersion are two crucial parameters to be determined as low as possible while designin... more Loss and dispersion are two crucial parameters to be determined as low as possible while designing optical fibers as optical transmission lines. In designing dispersion shifted fibers, one has to reduce the core diameter to smaller than unshifted single mode fiber (USMF) at 1550 nm wavelength region. This issue causes the nonlinear phenomenon of four wave mixing (FWM) to appear at 1550 nm. One of the approaches to reduce the effectiveness of the FWM is to shift the zero dispersion wavelength (ZDW) to some other wavelength in the third window of optical fiber communication. Dispersion compensating fibers (DCFs) with high negative dispersion are used in wavelength division multiplexing systems for neutralization of pulse spread in transmission fibers for higher system capacity. One of the approaches of securing a high negative dispersion is to change the refractive index profile of DCFs. In this paper, by using Optifiber software, the shifting of the ZDW is made by varying the refractive index profile of a USMF, then the designed profile is optimized for low dispersion and splice loss. The obtained results show that in designed profile the effective mode field diameter is reduced, which can effectively reduce the splice loss. In another attempt, the parameters of different DCF profiles are optimized to enhance negative dispersion of about -710 ps/nm.km, which is 5 times higher than the reported experimental results.
Bookmarks Related papers MentionsView impact
"In this paper, a single optical ring resonator connected to a Sagnac loop is used to demonstrate... more "In this paper, a single optical ring resonator connected to a Sagnac loop is used to demonstrate theoretically a novel narrow band optical filter response that is based on Sagnac phase-shift Df. The given filter structure permits the Sagnac rotation to control the filter response. It is shown that by changing the Sagnac rotation rate, we can tune the filter response for desired bandwidths. To increase the wavelength selectivity of the filter, the Sagnac phase-shift should be as small as possible that is
limited by the loop length. For Df ¼ 0.1 rad, the obtained FWHM is 2.63MHz for tuning loop length of 2 m. The simulation response agrees fairly with the recently reported experimental result.
Bookmarks Related papers MentionsView impact
A theoretical analysis of a tuneable optical filter is presented by proposing an optical ring res... more A theoretical analysis of a tuneable optical filter is presented by proposing an optical ring resonator (ORR) using photonic crystal fiber (PCF) as the resonance loop. The influences of the characteristic parameters of the PCF on the filter response have been analyzed under steady-state condition of the ORR. It is shown that the tuneability of the filter is mainly achieved by changing the modulation frequency of the light signal ap-plied to the resonator. The analyses have shown that the sharpness and the depth of the filter response are controlled by parameters such as amplitude modulation index of applied field, the coupling coefficient of the ORR, and hole-spacing and air-filling ratio of the PCF, respectively. When transmission coefficient of the loop approaches the coupling coefficient, the filter response enhances sharply with PCF parameters. The depth and the full-width half-maximum (FWHM) of the response strongly depends on the number of field circulations in the resonator loop. With the proposed tuneability scheme for optical filter, we achieved an FWHM of 1.55 nm. The obtained results may be utilized in designing optical add/drop filters used in WDM communication systems.
Bookmarks Related papers MentionsView impact
For characterisation of doped optical fibres (DOFs) based on single-beam
propagation, one requir... more For characterisation of doped optical fibres (DOFs) based on single-beam
propagation, one requires a maximum DOF length along which a signal power
can propagate. In this work we have solved the rate equation for the single-beam
propagation in both lossy and lossless DOFs, introduced an influence length as a
maximum propagation length and then determined it analytically. With the
analytical results obtained, the main regularities for the influence length have
been simulated for the glass optical fibres doped with Ge/Al/Er operating at
arbitrary wavelengths under lossless and lossy conditions. Also, the influence
length has been determined for some kinds of co-dopants present in both
polymer and glass optical fibres. The influence length thus defined may be useful
in any measurements based on the single-beam propagation in DOFs.
Bookmarks Related papers MentionsView impact
Optik, 2011
Bookmarks Related papers MentionsView impact
We proposed a novel model to evaluate the fluorescence and loss coefficients in the DOFs. This me... more We proposed a novel model to evaluate the fluorescence and loss coefficients in the DOFs. This method, can determine the loss and cross-sections of absorption and emission of DOFs, simultaneously, We named it as triple-cutback method.
Bookmarks Related papers MentionsView impact
Applied Physics B-lasers and Optics, 2010
We report a new simple technique for the simultaneous measurements of absorption-, emission cross... more We report a new simple technique for the simultaneous measurements of absorption-, emission cross-sections, background loss coefficient, and dopant density of doped optical fibers with low dopant concentration. Using our proposed technique, the experimental characterization of a sample Ge–Er-doped optical fiber is presented, and the results are analyzed and compared with other reports. This technique is suitable for production line of doped optical fibers.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Uploads
Papers by Faramarz E. Seraji
applied to a practical system and would be useful when dealing with analog optical fiber communication systems and optical
fiber sensing systems.
It is shown that, when temperature rises, the microbending loss and refractive index changes would decrease with increase of thickness of primary coating layer and will increase after passing through a minima. Increase of thickness of secondary coating layer causes the microbending loss and refractive
index changes to decrease.
We have shown that the temperature rise affecting the fiber makes the microbending loss and refractive index decrease, linearly. At a particular temperature, the microbending loss takes negative values, due to tensile pressure applied on the fiber.
The increase of Young’s modulus and the Poisson ratio of primary coating would lower the microbending loss and refractive index change whereas in the secondary coating layer, the condition reverses.
limited by the loop length. For Df ¼ 0.1 rad, the obtained FWHM is 2.63MHz for tuning loop length of 2 m. The simulation response agrees fairly with the recently reported experimental result.
propagation, one requires a maximum DOF length along which a signal power
can propagate. In this work we have solved the rate equation for the single-beam
propagation in both lossy and lossless DOFs, introduced an influence length as a
maximum propagation length and then determined it analytically. With the
analytical results obtained, the main regularities for the influence length have
been simulated for the glass optical fibres doped with Ge/Al/Er operating at
arbitrary wavelengths under lossless and lossy conditions. Also, the influence
length has been determined for some kinds of co-dopants present in both
polymer and glass optical fibres. The influence length thus defined may be useful
in any measurements based on the single-beam propagation in DOFs.
applied to a practical system and would be useful when dealing with analog optical fiber communication systems and optical
fiber sensing systems.
It is shown that, when temperature rises, the microbending loss and refractive index changes would decrease with increase of thickness of primary coating layer and will increase after passing through a minima. Increase of thickness of secondary coating layer causes the microbending loss and refractive
index changes to decrease.
We have shown that the temperature rise affecting the fiber makes the microbending loss and refractive index decrease, linearly. At a particular temperature, the microbending loss takes negative values, due to tensile pressure applied on the fiber.
The increase of Young’s modulus and the Poisson ratio of primary coating would lower the microbending loss and refractive index change whereas in the secondary coating layer, the condition reverses.
limited by the loop length. For Df ¼ 0.1 rad, the obtained FWHM is 2.63MHz for tuning loop length of 2 m. The simulation response agrees fairly with the recently reported experimental result.
propagation, one requires a maximum DOF length along which a signal power
can propagate. In this work we have solved the rate equation for the single-beam
propagation in both lossy and lossless DOFs, introduced an influence length as a
maximum propagation length and then determined it analytically. With the
analytical results obtained, the main regularities for the influence length have
been simulated for the glass optical fibres doped with Ge/Al/Er operating at
arbitrary wavelengths under lossless and lossy conditions. Also, the influence
length has been determined for some kinds of co-dopants present in both
polymer and glass optical fibres. The influence length thus defined may be useful
in any measurements based on the single-beam propagation in DOFs.