W. Weiershausen

Measuring the Link Distribution of PMD: Field Trial Using an RS-POTDR

A new POTDR measurement technique is used to investigate the spatial distribution of PMD in deployed fibers. Results help to identify high-PMD fiber sections that need to be replaced to enable 40Gbit/s transmission and beyond.

Analysis of Crosstalk in Mixed 43 Gb/s RZ-DQPSK and 10.7 Gb/s DWDM Systems at 50 GHz Channel Spacing

In DWDM field experiments over 1047 km of standard fiber and in simulations we analyze the impact of crosstalk on a 43 Gb/s RZ-DQPSK channel both by 10.7 Gb/s OOK and 43 Gb/s RZ-DQPSK neighbors at 50 GHz channel spacing.

Field trials with channel bit rates of 160 Gbit/s

We present two 8/spl times/170 Gbit/s DWDM/OTDM (1.28 Tbit/s) field transmission experiment both over more than 400 km in commercially operated legacy networks of France Telecom (FT) and Deutsche Telekom (DT), respectively. Conventional EDFA based amplification schemes as well as distributed Raman amplified systems are tested. For different levels of polarization mode dispersion due to different quality of the installed fibre infrastructure adaptive PMD compensation and polarization de-multiplexing is tested.

Characterisation of the PMD distribution along optical fibres by a POTDR

Fibre links in an optical network generally comprise several relatively short fibre segments which have been spliced together in cables. These fibre segments or ldquosectionsrdquo are assembled with optical connectors and have lengths of some tens of kilometres. The characteristic parameters of the fibre sections are attenuation, chromatic dispersion (CD) and polarisation mode dispersion (PMD). However, PMD of the optical fibres can hamper the upgrade of the optical b0ackbone network towards higher data rates of 40 Gbit/s and beyond. The PMD distribution along a buried fibre link is not a constant and can also significantly vary between the different fibres of the same optical cable. In the absence of such spatial information, the whole cable with higher PMD-values may have to be replaced in order to transmit 40 Gbit/s transparently over long distances. But investigations have shown that frequently localized pieces of the section are the major contributors to the overall high PMD value of the whole fibre, rendering the link unsuitable for higher data rates. A new random-scrambling polarization optical time domain reflectometry (POTDR) measurement technique is used to investigate the spatial distribution of the cumulative PMD in deployed fibres. Results help to identify high-PMD fibre pieces or sections which need to be replaced to enable 40 Gbit/s transmission and beyond, rather than substitution of a whole fibre link.

OTU3 Transmission with 43-Gbit/s-CS-RZ Signals over Installed G.652 Fiber Infrastructure and Accelerated PMD Outage Evaluation

A joint field trial on 40G transmission was conducted, where Deutsche Telekoms and NTTs R&D groups got involved. 43-Gbit/s/ch CS-RZ signals of the NTT G.709-OTN system were transmitted over selected high-PMD fiber links in DTs actual field environment. The advantage of CS-RZ modulation format was confirmed in comparison with conventional NRZ against all-order (first- and higher-order) PMD. Moreover, we introduced a new scheme for an accelerated determination of outage probability due to PMD that is adapted to practical field conditions in an operated fiber network with buried fibers and in-line operational optical elements.

Current developments and future perspective on technologies for system impairments and compensations

Due to increasing traffic demands telecommunication operators have to upgrade the transmission capacity of their networks. Since the success story of WDM in optical fiber based networks, component and system manufacturers as well as operators are dealing with the question if it is better to increase the number of WDM channels remaining at low channel bitrate or to enhance the channel line rate itself. The momentary situation is that already 10 Gbit/s based systems are installed for client traffic and are running properly. By a comparison of the technical advantages and business cases for a lot of transmission scenarios, the 10 Gbit/s solution turns out to be the preferable solution if compared to 2.5-Gbit/s-based systems. In the meantime 40GHz electronics has made severe progress so that now it seems to be possible to take the step towards the next hierarchy, the 40 Gbit/s channel rate. Nevertheless, many system manufacturers still wait with the market introduction of 40 Gbit/s, on the one hand because we observe a stagnant capacity demand this year, and on the other hand because the business case seems yet not to be competitive. One of the reasons for this is the impact of different physical limitations of fast optical fiber transmission. While the step from 2.5 to 10 Gbit/s still did not raise severe technological problems for medium distances, this is completely different for ultra long haul systems and especially for all 40-Gbit/s-based systems. While nonlinear effects still can be sufficiently managed, phenomena like, e.g., polarization-mode dispersion (PMD), chromatic dispersion mismatch, and gain tilt of optical amplifiers play an important role. Chromatic dispersion and polarization effects may vary with time so that either passive or adaptive compensation schemes may be needed in order to realize sufficiently long transmission distances. This paper will deal with different current solutions to overcome limitations from fibers and components, namely the use of special modulation formats, the use of pa