ALM5Q 1550 nm DWDM 10 mW 1 GHz Butterfly Analogue DFB Laser

The ALM5Q is intended for directly modulated broadband analogue links rather than coherent or externally modulated architectures. Its stated applications include CATV broadcast and narrowcast, DWDM forward paths, QAM transport and RF over fibre, supported by a minimum 1.1 GHz bandwidth and a nominal 25 Ω input impedance. Linearity figures include CNR of at least 51 dB, CSO limits of -50 or -52 dBc depending on fibre length, and CTB of up to -65 dBc. These figures use 79-channel loading, rated optical power, 25 °C operation and 0 dBm received power. Link performance should therefore be validated with the intended channel plan, fibre span, receiver and RF matching network.

Select the optical power first, then choose the required ITU channel from the wavelength list. The order-code diagram assigns XX to the 8, 10 or 11 dBm power option and ZZ to channels 12 through 59; 10 dBm corresponds to 10 mW, while 11 dBm is approximately 12.6 mW. The separate statement of up to 10 mW therefore conflicts with the 11 dBm option and should be resolved before production release. Wavelength selection must also account for the characterised operating range of 1529 to 1561 nm. The agreed power code, channel code and acceptance limits should be recorded in the component specification.

The laser requires closed-loop thermal control when stable wavelength and analogue performance are important. Its chip operating range is 15 to 35 °C, with an internal thermistor specified at 9.5 to 10.5 kΩ and a TEC operating envelope of -1.0 to 1.6 A under the stated condition. Cooler voltage is listed from -2.5 to 3.8 V, while the continuous absolute current limit is ±1.9 A. The controller should use current and voltage limiting, suitable loop compensation and protection against thermistor faults or open connections. Thermal margin must be checked at enclosure extremes because the characterised TEC case-temperature range is -20 to 65 °C, which differs from the storage range.

The RF interface should be designed around a nominal 25 Ω input rather than assuming a direct 50 Ω source match. The laser provides separate DC bias and modulation pins, with laser-common connections on pins 11 and 13, modulation on pin 12 and DC bias on pin 3. Operating current is specified up to 100 mA and operating voltage up to 2.1 V, while the minimum bandwidth is 1.1 GHz. A matching or transformation network may therefore be needed to control reflections, modulation depth and frequency response from the selected RF driver. The final layout should keep the modulation path short, provide the specified case grounds and verify linearity across the actual channel loading.

The analogue figures provide an initial link-budget reference, but they should not be treated as universal system results. CNR is listed at a minimum of 51 dB, CSO at a maximum of -50 dBc for the 10 km condition and -52 dBc for the 5 km condition, CTB at a maximum of -65 dBc, and RIN at a maximum of -155 dB/Hz. The distortion tests use 79-channel loading, rated optical power, 25 °C and 0 dBm received optical power. Receiver noise, fibre dispersion, connector losses and RF drive linearity can move the system result away from these values. Prototype testing should reproduce the intended fibre span and channel plan before design freeze.

The package combines the laser, optical isolator, TEC, thermistor and monitor photodiode in a hermetically sealed 14-pin butterfly body. Its standard pigtail is 1 m of SMF-28 fibre with a 0.9 mm flame-retardant Hytrel coating and an SC/APC connector, while nominal pin lead length is 5 mm from the package wall. Minimum optical isolation is 30 dB and minimum optical return loss is 40 dB. Mechanically, the design must protect the pigtail bend radius and avoid transferring connector strain into the package. Electrically, pins 8 and 9 provide case ground, while unused pins 10 and 14 should remain unconnected.

The maximum ratings are protection boundaries rather than normal operating targets. At the stated 35 °C rating condition, storage temperature is -40 to 85 °C, continuous forward laser current is limited to 150 mA, reverse laser voltage to 1 V and continuous TEC current to ±1.9 A. The monitor photodiode reverse-voltage limit is 10 V continuously or 15 V for 60 seconds. Driver start-up, shutdown and fault behaviour should prevent overshoot beyond these limits, particularly during TEC saturation or bias sequencing. ESD controls, current limiting and temperature interlocks should be defined at equipment level because no separate ESD rating is provided.

Not every wavelength in the ordering list falls inside the electro-optical operating range stated for the series. The ordering table covers channels 12 through 59, with wavelength entries from 1567.95 to 1530.33 nm, whereas the electro-optical table specifies 1529 to 1561 nm. Not all listed wavelengths are stated to be available, so channel availability and qualification status need confirmation for each order code. This is particularly relevant to the longer-wavelength entries above 1561 nm, where the two ranges do not align. For production control, require a confirmed wavelength, output-power code and acceptance limits on the purchase specification rather than relying only on the generic series code.