Data
sheet
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2.5 Gb/s Transmitter
Module - DWDM, 100 GHz
The MT25EW transmitter module provides an easy to use
self-contained optical source for Dense Wavelength Division
Multiplexed (DWDM) applications up to 2.7 Gb/s data rates.
The module requires +5 V, +3.3 V, 0 V supplies and
PECL/ECL data input to operate, and so allows non-DWDM
optical links to be upgraded very easily. Internal control
circuitry, including Etalon wavelength locking, ensures
that the optical source remains within optical power
and wavelength limits over variations in temperature,
power, and over life. The MT25EW conforms to ITU-T G.692,
ITU-T G.957, G.958 STM-16 Long Haul and Telcodia OC-48
Long Reach specifications for data links to 160 Km and
beyond. Over 40 wavelengths are available, specified
as per the ITU grid at 100 GHz channel spacing, covering
the C-band EDFA window.
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Features
Up to 2.7 Gb/s
ITU 100 GHz grid compliant
0 to +70C operation
High reliability optical components
Optical link lengths to 3000
ps/nm & beyond
Monitor functions for laser status
Laser disable function and
automatic mean power control
Source wavelengths available
covering the C-band
EDFA window
OPTICAL DEVICE
TXSD
DATA
DATA
LBC MONITOR
LASA (Laser alarm)
TEMP MONITOR
TEMP ALARM
Vcc
Vtec
Gnd
MODN INPUT
EIL FLAG
LASER DRIVE
AND CONTROL
CIRCUIT
THERMO-
COOLER
ELECTRIC
TEMP
CONTROL
CIRCUIT
MONITORS
& ALARMS
CIRCUIT
Figure 1: Transmitter block diagram
Functional description
The module comprises an hermetically packaged 1550 nm BH Laser device with optical isolation and
Etalon wavelength feedback, laser drive, automatic laser power control, and monitoring circuitry.
The laser package uses a Thermo-Electric Cooler (TEC) to maintain the correct laser temperature to achieve
constant lasing wavelength based on true wavelength feedback from the Etalon filter. The microprocessor
based control circuit also provides temperature monitoring, alarm outputs and internal fault diagnostics.
The module features high speed complementary data inputs which are AC coupled and have internal 50
termination, transmitter disable input, modulation input for wavelength tagging, alarm and monitor
supervisory outputs, Etalon in lock output flag.
The optical output is via a single mode pigtail which can be fitted with a variety of single mode
optical connectors.
The module operates from a 5 V supply, with 3.3 V supply for the TEC to minimise power dissipation. The
module is very compact and incorporates an advanced integral heatsink.
Transmitter operation
Optical power control
The on board microprocessor provides fully automatic integrated power and wavelength control using
the Etalon output signals as feedback. This approach enables a controlled start and inter-channel
protection as well as normal constant power control.
Data input (DATA, DATA)
The inputs are AC coupled and terminated with 50
. This provides 100
differential impedance. The
recommended input signal must meet the required voltage swing for PECL/ECL. Due to the high speed
nature of this product it is vital that high speed design rules are followed in the design of the system board.
Follow the recommended user interfaces.
This transmitter is not suitable for burst mode operation and unbalanced data patterns may affect the
automatic constant power circuit.
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Transmitter operation (continued)
Transmitter disable (TXSD)
Transmitter operation can be disabled by applying a CMOS Logic 1 level to the TxSD pin. The laser can
be disabled by the module microprocessor in the event of gross failure. When disabled the output power
is < -40 dBm. In event of the microprocessor sets the Laser Alarm and the Temperature Alarm and
maintains the transmitter disable until a power on reset.
Laser Bias Current Monitor (LBCM)
The LBCM provides an analog voltage output corresponding to the laser bias current. The LBCM output
is referenced to ground and indicates the change of laser threshold as the laser ages. The LBCM output
is buffered; use with high impedance loads to reduce errors and dissipation.
Laser alarm (LASA)
The Laser Alarm is an Active High CMOS level output. The Laser Alarm is active when the optical
output power is outside of operations limits.
Temperature alarm
The temperature alarm is an active high CMOS level output. The temperature alarm is activated when
the laser temperature is approximately 1C above or below normal laser operating temperature for
Etalon lock. This is a high current output and can drive alarms directly.
Etalon in lock flag (EILF)
This output provides an indication of when the wavelength is locked to the reference wavelength under
Etalon control.
Modulation input (MODN)
The modulation input allows for the use of a low frequency tone (10-500 kHz) for modulation of
the "1"s level. This input must be driven from a 50
source, and is AC coupled internally. Do not
exceed the maximum drive level. Over driving this input can cause waveform distortion; limit
modulation depth to 5-10%. If unused, connect this input to 0 V to prevent noise pickup.
Two-wire interface (TWCK, TWDA)
The module can be configured using a two-wire communication interface. TWCK carries the clock
signal generated by the external master. TWDA carries the serial data stream.
Power supplies
The module operates from a single rail power supply of +5.0 V nominal. The Thermo-Electric Cooler is
supplied from a separate pin (Pin 11 Vtec). The TEC operates with a 3.3 V supply for a wide operating
temperature range. This low voltage ability is used to reduce the power dissipation of the module.
Ensure the supply to the module is well filtered and as noise free as possible to prevent any possible
interference with the module (see the recommended system interface). The supply feeds to the module and
TEC must be of low DC impedance with minimal voltage drop at the maximum module and TEC currents. For
maximum EMI screening, the case is electrically connected to the Gnd pins.
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Specification
Stresses beyond those in Table 2: "Absolute maximum
ratings" may cause permanent damage to the module.
These are stress ratings only and functional operation
of the module at these or any other conditions beyond
those indicated in the operational sections of the
specifications is not implied. Exposure to absolute
maximum rating conditions for extended periods may
affect the module's reliability.
Pin #
Name
Pin #
Name
1
Gnd
20
Two-wire Data
2
Data
19
Two-wire Clock
3
Data
18
Gnd
4
Gnd
17
Vcc
5
Laser Disable
16
Vtec
6
Vcc
15
Temperature Alarm
7
Vcc
14
No internal connection
8
Vcc
13
Laser Alarm
9
Modulation Input
12
Laser Bias Current Monitor
10
Gnd
11
Etalon in Lock Flag
Pinout
Table 1: Module pinout
Parameter
Min
Max
Unit
Operating Case Temp
0
+70
C
Shipping/storage Temp
-40
+85
C
Relative Humidity
95
%RH
Applied Voltage(Any Pin)
-0.5
6.0
V
Lead Soldering Temp
250
C
Lead Soldering Time
10
S
Fibre Bend Radius
30
mm
Table 2: Absolute maximum ratings
Gnd pins are connected to the module case. Do not make any connection to pin 14.
Pins 19 & 20 can be connected to ground if not using the two wire interface.
Physical dimensions
Parameter
Min
Max
Unit
Bend Radius
30
mm
Mode Field Diameter
8.8
9.8
m
Cladding Diameter
122
128
m
Concentricity Error
0.5
m
Pigtail Length (Typical)
1
950
1050
mm
Table 3: Fibre pigtail
Note 1: Other pigtail Fibre lengths available on request
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Figure 2: Mechanical outline
Mechanical outline
All dimensions in mm unless otherwise stated, general tolerance = 0.25 mm
Electrical characteristics
The product is intended for use in fully compliant STM16 Long-haul optical links. These are defined by ITU-T G.957,
G.958, and G.692. It is also intended for use in OC48 Long/Intermediate reach optical links as defined by Telcodia
TA-NWT-000253. Table 4 shows the power supply requirements and digital data levels which must be met over
temperature and life.
Typical parameters are RT/SOL, MIN and MAX values are over the operating temperature and power supply range.
Data input is 2.488 Gb/s 2
23
-1 PRBS NRZ. PECL 10K
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