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network-electronics.com
40-ch 100GHz Dense Wavelength
Division Multiplexing System
Rev. 0
Flashlink User Manual
DWDM-40C
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DWDM-40C Rev. 0
Network Electronics ASA
Thorøya
P.O. Box 1020
N-3204 Sandefjord, Norway
Phone: +47 33 48 99 99
Fax: +47 33 48 99 98
Email:
support@network-electronics.com
www.network-electronics.com
Support Phone: +47 90 60 99 99
Revision history
Current revision of this document is the uppermost in the table below.
Rev. Repl. Date Sign Change description
0 - 2007-11-20 OEH New manual released
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DWDM-40C Rev. 0
Contents
Revision history .......................................................................................................... 2
1 Product overview ..................................................................................................... 4
2 Specifications .......................................................................................................... 5
2.1 Optical specifications for 40-channel system .....................................................................5
2.2 Wavelength Chart according to ITU-T G.694.1 ..................................................................6
3 Connections............................................................................................................. 7
3.1 Connecting to the DWDM-40C...........................................................................................7
3.2 System design....................................................................................................................7
4 Operation................................................................................................................. 8
4.1 Handling of optical fibers ....................................................................................................8
4.2 Laser safety precautions ....................................................................................................8
4.3 Connector cleaning ............................................................................................................9
4.4 Power dissipation in the DWDM-system. ......................................................................... 10
General environmental requirements for Network Electronics equipment ................ 12
Certificate of Conformity .............................................. Error! Bookmark not defined.
Product Warranty...................................................................................................... 13
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1 Product overview
The Flashlink DWDM-40C is a set of optical modules for multiplexing and demultiplexing
100GHz spaced DWDM (Dense Wavelength Division Multiplexed) signals. The modules are
bidirectional, so they work as both multiplexer and demultiplexer at the same time.
A DWDM-40C consists of one DWDM-40C-A and one DWDM-40C-B, which when used
together, provide an optimal link loss by stepping the insertion loss profiles in one end point
complementary to the other.
Figure 1: DWDM-40C block diagram
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2 Specifications
2.1 Optical specifications for 40-channel system
Number of channels
40
Available wavelengths
See section
0
Connector
SC/UPC
Insertion loss (per matched pair,
including connectors)
6dB max
Channel Spacing
100GHz
Passband ITU +/- 12.5GHz
Adjacent Channel Isolation 25dB min (28dB typ.)
Non-Adjacent Channel Isolation 40dB min
Directivity 45dB min
Thermal Wavelength Stability 1.0 pm/
o
Cmax
Return loss 45dB min
PDL 0.25dB max
Operating Temperature 0 – 40
o
C
Storage Temperature -40 – 85
o
C
Optical Power 300mW max
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2.2 Wavelength Chart according to ITU-T G.694.1
The following wavelengths/channels are in use for the 40 channel system DWDM-40C
ITU Channel
No.
Frequency
[THz]
Wavelength
[nm]
59 195,90 1530,33
58 195,80 1531,12
57 195,70 1531,90
56 195,60 1532,68
55 195,50 1533,47
54 195,40 1534,25
53 195,30 1535,04
52 195,20 1535,82
51 195,10 1536,61
50 195,00 1537,40
49 194,90 1538,19
48 194,80 1538,98
47 194,70 1539,77
46 194,60 1540,56
45 194,50 1541,35
Blue wavelengths
44 194,40 1542,14
43 194,30 1542,94
42 194,20 1543,73
41 194,10 1544,53
40 194,00 1545,32
39 193,90 1546,12
38 193,80 1546,92
37 193,70 1547,72
36 193,60 1548,51
35 193,50 1549,32
34 193,40 1550,12
33 193,30 1550,92
32 193,20 1551,72
31 193,10 1552,52
30 193,00 1553,33
29 192,90 1554,13
28 192,80 1554,94
27 192,70 1555,75
26 192,60 1556,55
25 192,50 1557,36
24 192,40 1558,17
23 192,30 1558,98
22 192,20 1559,79
21 192,10 1560,61
20 192,00 1561,41
Red wavelengths
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3 Connections
3.1 Connecting to the DWDM-40C
Figure 2.11 shows the backplane for the flashlink 40-channel DWDM optical filter frame.
Each optical port supports a dedicated wavelength that is marked on the sub-rack frame. The
connector is an SC/PC connector. Each port should be connected to the corresponding
wavelength for each channel card with an optical patch cord. The common port supports all
wavelengths in either direction and should therefore be connected to the single fiber between
the two locations where the flashlink 40-channel DWDM system is installed. The optical
filters are sold in pairs using cascaded thin film filters for wavelength selection. This means
that the filters are mounted in opposite orders on the two sides. Those wavelengths which
have lower attenuation in one end point have higher attenuation in the other end point, thus
ensuring all channels have the same link loss. The specification of the optical filters can be
found in chapter 2. One side is marked DWDM-40C-A, the other is marked DWDM-40C-B.
Figure 3.1: The backplane for the 40-channel DWDM system optical filter (endpoint A)
3.2 System design
The maximum insertion loss for any channel in end point A is 4.0dB, but the same channel in
the complementary end point B will then have a maximum insertion loss of 1.5dB. Likewise
the channel with maximum allowed insertion loss of 1.5dB in endpoint A will have a
maximum insertion loss of 4.0dB in end point B. This means that there can theoretically be
about 3dB difference in attenuation between two different channels (1.5dB variance across
the band) after multiplexing. When using erbium doped fiber optical amplifiers (EDFA), this
can lead to large differences in signal strength between different channels at the receiving
end. The reason is that EDFAs also have a variance in gain across the wavelength band.
Therefore a special uniform loss version (suffix -U) is available as an option.
EDFAs used with DWDM-40C should have a gain flattening filter and operate close to
nominal gain / input power. When operating over or under nominal gain, the EDFAs gain
variance changes drastically.
The minimum headroom that needs to be considered when designing a system increases for
each EDFA because of the gain variance across wavelengths.
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4 Operation
4.1 Handling of optical fibers
This product includes fiber optic equipment. Access to the optical signal path is given through
the optical connectors (see separate chapter).
Even though a fiber optic cable can look almost the same as an electrical wire, special care
must be taken. Inside the cable is a fiber made of glass. Glass has very different physical
properties than the copper used in electrical wires.
In practical terms this means that these precautions must be taken:
• Do not bend the fiber too much
• Do not put anything on top of the optical fiber.
• Keep the connectors clean from dust
If a fiber is bent to much, parts of the transmitted light is lost or in worst case the glass is
broken. All the datasheets of optical fibers have a point called "minimum bend radius". This
means that any bending of the fiber corresponding to a bend radius less than the given value
will make the light leak out of the fiber. A typical value is 20 mm to 40 mm (Telcordia
standard) for single mode fibers.
You should also avoid putting any heavy items on top of the optical fibers, because this will
change the optical properties of the fiber, and contribute to errors in the transmitted signal.
Unless the fiber is damaged, it will regain its optical properties after a bend is straightened
out or the items are removed / the squeeze is released.
4.2 Laser safety precautions
Guidelines to limit hazards from laser exposure.
All the available EO units in the flashlink
®
range include a laser.
Therefore this note on laser safety should be read thoroughly.
The lasers emit light at wavelengths around 1550 nm. This means that the human eye
cannot see the beam, and the blink reflex cannot protect the eye. (The human eye can see
light between 400 nm to 700 nm).
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A laser beam can be harmful to the human eye (depending on laser power and exposure
time), therefore:
!! BE CAREFUL WHEN CONNECTING / DISCONNECTING FIBER PIGTAILS
(ENDS).
NEVER LOOK DIRECTLY INTO THE END OF THE FIBER.
NEVER USE MICROSCOPES, MAGNIFYING GLASSES OR EYE LOUPES TO LOOK
INTO A FIBER END.
USE LASER SAFETY EYEWEAR BLOCKING LIGHT AT 1310 nm AND AT 1550 nm.
Instruments exist to verify light output power: Power meters, IR-cards etc.
The FR-2RU-10-2 is classified as Class 1 laser product according to EN 60 8251:94/A11:96, and CFR Ch1(1997) Part 1040.10.
If the front panel is removed, the FR-2RU-10-2 is classified as Class 1 laser product
according to EN 60 825-1:94/A11:96, and class IIIb according to CFR Ch1(1997) Part
1040.10.
Maximum output power after multiplexing in DWDM-40C: 30mW
Operating wavelengths: 1550 ± 20nm.
< 5mW
>1270nm
4.3 Connector cleaning
Optical connectors should be kept clean at all times. Whenever a connector is disconnected
the enclosed protective dust cap should be put on. This protects the ferrule used for fiber
alignment and prevents the surface from being scratched or damaged.
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Figure 1.1: The different parts of an SC/PC connector
Cleaning procedure:
If the ferrule is dirty it must be cleaned before re-connection.
If a clean connector is pressed against a dirty connector, both connectors will become dirty
resulting in possible degradation of signal quality. Or even worse, you may damage the
surface of the connector(s). We recommend that the cleaning procedure is done by using a
special cleaning-tape suitable for this purpose, called CleTop (see picture below).
4.4 Power dissipation in the DWDM-system.
Due to the need of very stable laser emission wavelengths, a precise temperature control of
the laser cavity is needed. The laser wavelength will drift with changing temperature if the
laser is not controlled. This means that the internal temperature of the laser must be kept at a
constant level for all operation temperatures.
This is done through the use of a Peltier element placed within the laser package. The
function of the Peltier element is to control the temperature in a similar way as a refrigerator.
If the ambient temperature increases the Peltier element will cool the inside of the laser
package to keep the temperature at a constant level. If the opposite is the case and the
ambient temperature decreases, the Peltier element will heat the inside of the package to
keep the internal temperature constant. The quantity of heat absorbed or produced is
proportional to the current flowing through the contact. In practical terms this means that the
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current is proportional to the temperature difference between the ambient temperature and
the desired temperature within the laser package.
If the ambient temperature is lower than the package temperature, the power dissipated will
support the heating process of the device by increasing the ambient temperature. On the
other hand, if the ambient temperature is much higher than the desired package temperature
(about +22°C) it may cause the laser to malfunction. The current, which is proportional to the
temperature difference, implies power dissipation and an increase of the ambient
temperature.
This increased ambient temperature will again increase the current through the Peltier
element in order to lower the internal package temperature. The increased current will make
more power dissipate thereby increasing the ambient temperature, and so on.
To avoid this, proper ventilation of the DWDM-system is needed. A 40-channel system needs
12RU-26ru of rack space. Additional rack space needed for ventilation is 1RU above and
below each set of 4 flashlink frames (8RU). Receiver cards generate less heat than
transmitter cards, and bidirectional cards decrease the number of cards in a 40-channel
system. Please consult with Network Electronics before building a 40-channel system.
Example with 6 flashlink frames, frame space utilisation depending on card types:
1RU Fan, hot air exhaust
6RU 3x flashlink DWDM frames
1RU Cold air intake
2RU flashlink DWDM filter frame
1RU Fan, hot air exhaust
6RU 3x flashlink DWDM frames
1RU Cold air intake
The operational temperature for the DWDM-system is 0°-40°C.
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General environmental requirements for Network Electronics
equipment
1. The equipment will meet the guaranteed performance specification under the following
environmental conditions:
- Operating room temperature range: 0°C to 40°C
- Operating relative humidity range: <90% (non-condensing)
2. The equipment will operate without damage under the following environmental
conditions:
- Temperature range: -5°C to 50°C
- Relative humidity range: <95% (non-condensing)
3. Electromagnetic compatibility conditions:
- Emissions: EN 55103-1 (Directive 89/336/EEC)
- Immunity: EN 55103-2 (Directive 89/336/EEC)
- Electrical safety: EN 60 950
With reference to the declaration of conformity provided with the external power supply.
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Product Warranty
The warranty terms and conditions for the product(s) covered by this manual follow the
General Sales Conditions by Network Electronics ASA. These conditions are available on the
company web site of Network Electronics ASA:
www.network-electronics.com
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