In the work, the intensity and phase modulation methods are compared for different versions of the wavelength division multiplexing (WDM) system. Binary and multilevel code formats are evaluated ...numerically, with OptSim simulation software at the bit rate of 10 and 40 Gbit/s, using long-fiber spans and dispersion compensation technique. The problems to be overcome at exploitation of multiterabit WDM systems based on 40 Gbit/s optical transmissions are: chromatic dispersion (CD), polarization-mode dispersion (PMD), dispersion slope, and nonlinear effects of the transmission line. We have investigated the potentialities of modulation formats for 40 Gbit/s WDM networks where most of the listed problems are avoided. It is shown that Duobinary and differential phase shift keying (DPSK) modulation formats are perfectly suitable for ultra-high spectral efficient WDM systems and possess high resistance to dispersion and nonlinear optical effects (NOE).
Darbā pētītas un salīdzinātas intensitātes un fāzes modulācijas metodes optiskajās spektrālās blīvēšanas (WDM) sistēmās. Binārie un daudzlīmeņu kodēšanas formāti ir skaitliski novērtēti ar simulācijas programmatūras OptSim palīdzību pie 10 Gbit/s un 40 Gbit/s pārraides ātrumiem, izmantojot garas optiskās šķiedras līnijas un dispersijas kompensēšanas tehniku. Galvenās problēmas, kas ekspluatācijas laikā ir jāņem vērā sistēmās ar pārraides ātrumu līdz 40 Gbit/s, ir hromatiskā dispersija (CD), polarizācijas - modu dispersija (PMD), dispersijas slīpums un pārraides līnijas nelineārie efekti. Novērtēti perspektīvākie modulācijas formāti 40 Gbit/s WDM sistēmām. Pētījumā uzskatāmi demonstrēts, ka daudzlīmeņu modulācijas un diferenciālās fāzes manipulācijas (DPSK) formāti ir atbilstošākie liela ātruma spektrāli efektīvām sistēmām. Tos var raksturot ar augstu noturības līmeni pret dispersiju un nelineārajiem optiskajiem efektiem (NOE).
Efficient Wavelength Filters for DWDM Systems Ozolins, O.; Bobrovs, V.; Ivanovs, G.
Latvian journal of physics and technical sciences,
01/2010, Volume:
47, Issue:
6
Journal Article
Peer reviewed
Open access
The authors investigate the best parameters of optical filters for dense wavelength division multiplexing (DWDM) systems. The investigation is based on the OptSim 5.0 simulation software using the ...method for solving a complex set of differential equations taking into account the optical and electrical noise as well as linear and nonlinear effects. It is shown that the bandwidth of optical filter extends as the data transmission speed increases, and that the most efficient are Supergaussian and Raised Cosine optical band-pass filters. It is also revealed that an ASK-RZ 40 Gbit/s data transmission system is impossible to realize with a channel interval less than 50 GHz because of wide spectral density and lower chromatic dispersion tolerance of this modulation format.
Autori ir noskaidrojuši labākos optiskā filtra parametrus blīvām viļņgarumdales blīvēšanas (DWDM) sistēmām. Pētījumi ir realizēti ar OptSim 5.0 simulācijas programmatūru, kuras izmantotā aprēķinu metode balstās uz sarežgītu diferenciālvienādojumu risināšanu, ņemot vērā optisko un elektrisko troksni, lineāros un nelineāros optiskos efektus. Pētījumā parādīts, ka optiskā filtra joslas platums palielinās līdz ar datu pārraides ātrumu, un noskaidrots, ka Supergausa un Pacelta Kosinusa optiskie joslas filtri ir efektīvākie. Savukārt, ASK-RZ 40 Gbit/s datu pārraides sistēmu nav iespējams realizēt ar kanālu intervālu, kas mazāks par 50 GHz, tā plašā jaudas spektrālā blīvuma un zemās hromatiskās dispersijas noturības dēļ.
Thermal lensing in relaxor type ferroelectrics as a function of temperature has been investigated by using pulse/probe method. Enhanced thermo-optical (TO) properties had been observed in 3d elements ...(Cu, Co) doped PLZT ceramics and in sodium-bismuth titanate single crystals near phase transitions (PT). Comparison of TO signals for several doped PLZT materials reveals that 0.5 wt.% Cu doping is responsible for improved thermal lensing parameters interpreted by optimal light absorption, heat transfer and possible PT adjustment. TO experiments in sodium-bismuth titanate single crystals (001 cut) show enhancement of TO properties in the region of PT and coexisting phases (rhombohedral and tetragonal).
The paper presents an overview of widely accepted passive optical networks (PONs), and provides the results of comparative OPTSIM simulation for PON technological facilities involving optical layers, ...with the aim to reveal fiber-to-the-x (FTTx) technologic solutions. Traffic load is simulated over a PON optical layer using the OPNET Modeler to determine potential advantages and drawbacks of the proposed FTTx solution with PON elements in the access networks. The authors show that the optimal transmission speed for PON FTTx would lie in the range 1.25-5.0 Gbit/s with a standard PON architecture, which could be raised to 10 Gbit/s, however in this case we have to change the end user's equipment. In standards that specify the PON's functionality two distances: 10 km and 20 km are indicated. Our simulation shows that, after upgrading the receiver electrical filter, 10 Gbit/s transmissions over 40 km could be reached.
Darbā, ar OPTSIM simulācijas programmatūras palīdzību pētītas un salīdzinātas vairākas pasīvas optisku tīklu (POT) arhitektūras. Novērtēti tehnologiskie risinājumi dzīslā līdz x (DLx) fiziskajam slānim. Trafika simulācijas ir veiktas ar OPNET Modeler programmatūru un ir izveidotas rekomendācijas DLx sistēmas realizācijai. Autoru pētījums ir pamatots ar nepieciešamību integrēt jaunas sistēmas jau esošajos POT risinājumos. Pētījumā uzskatāmi demonstrēts kā optimālais pārraides ātrums POT DLx sistēmās atrodas starp 1,25 Gbit/s un 5 Gbit/s standartiem POT risinājumā. Mainot klienta gala aparatūru, iespējams paaugstināt ātrumu līdz 10 Gbit/s un palielināt attālumu no 20 līdz 40 km, nemainot visu POT arhitektūru, bet mainot tikai uztvērēja bloka elektrisko filtru.
The maximum reach of the Dense Wavelength-Division-Multiplexed Passive Optical Network (DWDM-PON) system can be severely limited by chromatic dispersion (CD). This paper contains the investigation of ...long-reach high speed 16-channel DWDM-PON system with efficient CD compensation methods. It is shown that chromatic dispersion compensation has a crucial role for guaranteed downstream optical link performance and maximum link length of high speed long-reach DWDM-PON system. The results show that usage of additional 7 km long dispersion compensating fiber (DCF) placed in central office improves the DWDM-PON network reach by 19.3% (from 57 km up to 68 km) but usage of fiber Bragg grating (FBG) improves network reach up to 26.3% (from 57 km up to 72 km). As a result, authors recommend the use of FBG for chromatic dispersion compensation to increase the maximum transmission distance of high speed DWDM-PON system.
The present paper proposes the optimal transmission parameters for non-return-to-zero (NRZ), return-to-zero differential phase shift keying (RZ-DPSK), carrier-suppressed RZ-DPSK (CSRZ-DPSK) and ...duobinary (DB) modulation formats in 16-channel 10 Gbit/s wavelength division multiplexed passive optical network (WDM-PON) transmission system. The paper investigates influence of laser output power, length of dispersion compensating fiber (DCF) and application of erbium-doped fiber amplifiers (EDFA), as well as impact of optical components configuration on received signal quality. It compares demand of these modulation formats for amplification and dispersion compensation with the increase of transmission distance, determining the optimal conditions for achieving maximal network reach for each of them. It is shown, that DB is the most resistant to chromatic dispersion (CD) and is able to achieve the longest transmission distance (100 km) without dispersion compensation. Whereas RZ-DPSK and CSRZ-DPSK modulation formats demonstrated maximal achievable reach (180 km) using DCF and EDFA.
In this paper the authors demonstrate a model of a multicarrier light source for wavelength division multiplexed transmission systems, where two dual-pump fiber optical parametric amplifiers are used ...to increase the number of initial carriers three times. The optical radiation of the 16 initial carriers is combined and afterwards divided among the two parametric amplifiers, which are placed in parallel in the scheme. Each amplifier is responsible for generating 16 additional carriers that afterwards will be used as transport for the informative signal. The proposed multicarrier source solution allows to produce 48 carriers with 100 GHz channel spacing and with power non-uniformity below 2 dB among all the channels at the output of the transmitter.
This paper contains the investigation of 8-channel wavelength-division-multiplexed passive optical network by using spectrum-sliced amplified spontaneous emission (ASE) source as a seed light with ...arrayed-waveguide gratings (AWGs). There are investigated the impact of signal filtering for Gaussian and Flat-top type AWGs on the overall optical system's performance. It is shown that Gaussian type AWG's with channel interval 100 GHz are not suitable for SS-WDM PON systems with high data rate - 2.5 Gbit/s because of wide spectral shape and high channel crosstalk. Numerically it is proved that best solution for 8 channel SS-WDM PON system which provides high performance over the passive fiber optical link length up to 10 km with BER <; 1·10 -10 are AWG's with Flat-top spectral shape. It has been investigated that Flat-top AWG unit shows high OSNR because of its amplitude transfer function that provides excellent channel separation and filtering at the same time passing sufficient high optical power from spectrally sliced ASE broadband light source.
The format conversion with a single uniform fibre Bragg grating of 40 Gbit/s return to zero on-off keying to nonreturn to zero on-off keying has been demonstrated numerically for the first time. ...Error free performance is achieved for uniform fibre Bragg grating with different reflectivity values.
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