Testing and Deployment of CLM 2×16+16×2 and CLS/M in the CESNET Experimental Facility

CESNET technical report 19/2010

Jan Radil, Lada Altmannová, Miloslav Hůla, Jan Nejman, Stanislav Šíma, Pavel Škoda, Tomáš Uhlář, Josef Vojtěch

Received 1. 12. 2010

Other formats: PDF, EPUB

Abstract

This technical reports deals with practical results of testing and deployment of new advanced photonic devices from the CzechLight (CL) family of open photonic devices. CLM 2×16+16×2 is an optical switch with multicasting capabilities. Such a device can be used to multicast and distribute high speed optical signals like high definition (HD) video, 4k aka digital cinema or rather special signals like accurate time or frequency. Other tested device is CLS/M which is an optical switch with multicasting, switching and monitoring capabilities, with variable ratios.

Keywords: optical multicast, all-optical processing, experimental facility, accurate time

1 Introduction

The CLM 2×16+16×2 is a device capable of all optical multicast, with two input ports and 16 output ports in one direction and back channel switching, which is very useful for setting of bidirectional video transmission (transceivers need bidirectional connections). More information on CLM 2×16+16×2 can be found online [1]. The first device with the same optical multicasting capabilities was the CLM 4×4 device (four input and four output ports, protected by the Czech patent), used in two international GLIF demos [2].

What was apparent during those two GLIF demos was that the number of the input ports could be smaller. One would be sufficient for many applications when only one HD or 4k video transmitter is available. On the other hand, more output ports would be beneficial and were requested by some researchers. Based on these requests, it was decided that a new CLM device is needed and the number of input ports was set to be 2 (as one may be too limiting in case of failure) and the number of output ports is 16, which is enough for today’s advanced applications.

CLS/M is an optical fibre switch with both switching and multicasting capabilities (patent pending). This means optical monitoring is very easy, especially because of variable ratios: signals can be splitted in any ratio between 0% and 100%. The CLS/M is available in two models: 8×8 and 16×16. Operational band is C only but switching speed is 3 ms. Insertion loss is dependent on configuration used and is 4-13 dB and 5-17dB for 8×8 and 16×16 models, respectively. CLS/M devices are based on non-mechanical, planar lightwave technology and utilize pulse-width modulation (PWM) to achieve continuous and variable splitting ratios of optical signals (technical details are considered to be out of scope of this report).

Figure 1. Some possible configurations of CLS/M. The first one is just multicasting of 4k video streams, the second one is monitoring of noise and residual chromatic dispersion for these 4k video streams.

Figure 2. The working sample of the CLS/M 16×16.

A rather new area of applications is transfer of accurate time and frequency. Such applications are gaining momentum and this fact is also recognized for example by Geant network engineers for future network planning. Researchers from CESNET have developed and tested a new device for transfer of accurate time and more details can be found online at [3]. Distribution of such signals cannot be achieved with classical devices which include OEO conversions. The reasons are twofold: OEO devices capable to work with such signals (i.e. 4k or accurate time) are not commercially available and requirements for low and predictable network latency are rather strict and therefore all optical signal processing is the only possible option.

2 Testing and Deployment

The CLM 2×16+16×2 and CLS/M devices have all the features as other CL devices. Can be accessed over an IP network and other ways are possible too (e.g. GSM modem). Secure shell (SSH) is implemented and access is limited to particular IP addresses or networks. For operation (setting and reading of any parameter), the shell scripts are prepared and used. Web access is possible if requested by users.

CLM 2×16+16×2 was used for transmission and multicasting of HD video signals in the past and in this report we’ll present results of transmitting time stamps by means of customized HW developed by CESNET [4]. As with any other testing of new CL devices, firstly it was tested on fibre spools in the lab and results were very good. Then it was tested on a dark fibre link between CESNET and Institute of Photonics and Electronics, Academy of Sciences, with the length 15 km of standard G.652 fibre. Results of transmission were OK, if the time stamp signal is multicasted 1:16, additional optical amplifiers can be used to maintain sufficient power levels for different types of optical receivers.

Figure 3. Input signal of accurate time used for CLM 2×16+16×2 experiments.

Figure 4. Output signal of accurate time after passing CLM 2×16+16×2, with full multicast 1:16.

Many tests and measurements were performed for the CLS/M 8×8 and 16×16 devices. For example matrix uniformity and different multicasting configurations were measured and recorded very precisely (up to 65k measured points). Results will be used not only in CESNET but in the GN3 project too. Results shown on Figures 5–8 were measured for CLS/M 16×16.

Figure 5. Attenuation as function of PWM between input 1 and measured for all outputs (1-16), 65535 measured points, 16 curves total.

Figure 6. Attenuation as function of PWM between all inputs (1-16) and measured for all outputs (1-16), 16384 measured points, 256 curves total.

Figure 7. Attenuation as function of PWM, testing signal fed on all inputs and measured for all outputs (1-16) but only maximal, minimal (both measured) and average (calculated) curves are displayed.

Figure 8. CLS/M used as variable multiplexes, 3 signals on inputs 1, 2 and 3 are switched to output 5.

3 Conclusions

The new advanced open photonic devices CLM 2×16 +16×2 and CLS/M 8×8 have been successfully tested and deployed in the CESNET Experimental Facility. All stabile and proven SW features known from previous deployment of the CLM 4×4 are embedded in these devices too.

Deployment of these devices can be recommended for any application requiring all optical processing with low and predictable latency.

4 Acknowledgements

This work has been supported by the research intent Optical Network of National Research and Its New Applications, MŠMT 6383917201.

References

[1]	ALTMANNOVÁ, L. et al. Optické sítě. In SATRAPA, P. (ed.). Optická síť národního výzkumu a její nové aplikace 2009: Roční zpráva o řešení výzkumného záměru.. Praha: CESNET, 2009. ISBN 978-80-904173-6-6. Available online.
[2]	RADIL, J.; ŠÍMA, S. Customized Approaches to Fibre-based E2E Services. In 1st E2E Workshop – Establishing Lightpaths, 1-2 December 2008. TERENA. Available online.
[3]	A new method of accurate time signal transfer demonstrates the capabilities of all-optical networks. Press release, 1 April 2010, Praha: CESNET. Available online.
[4]	SMOTLACHA, V.; KUNA, A.; MACHE W. Time Transfer in Optical Network. In Precise Time and Time Interval Systems and Applications Meeting (PTTI) 2010, Reston, USA.