ALM938 1530-1560 nm 60 mW Butterfly CW DFB Laser

Yes. The ALM938-60 is intended to act as a narrow-linewidth CW source ahead of an external modulator, including a LiNbO₃ Mach-Zehnder device. Its spectral linewidth is limited to 1 MHz, while relative intensity noise is specified at no more than −157 dB/Hz across 20–1000 MHz and side-mode suppression is at least 30 dB. The 60 mW output option provides optical power for links that include loss-producing passive or active components. A minimum 18 dB polarisation extinction ratio and PMF output also support polarisation-sensitive modulator interfaces. Link gain, noise figure and modulator optical-power limits still need to be checked at system level.

A closed-loop TEC controller should use the integrated 10 kΩ thermistor, whose specified resistance range is 9.5–10.5 kΩ. During operation, the TEC interface may require current from −1.2 to +1.2 A and voltage from −2.5 to +2.5 V, with the cooler-voltage condition given for a 15–35 °C operating temperature over the case-temperature range. The permitted case range is 0–65 °C, wavelength drift with case temperature is limited to 0.001 nm/°C, and temperature tracking error is ±0.5 dB. The controller therefore needs bidirectional current capability, adequate voltage compliance and stable thermistor sensing. Thermal design should also keep normal operation below the separate ±1.9 A absolute TEC rating.

The laser-current driver should accommodate up to 500 mA at up to 2.1 V, while maintaining sufficiently low electrical noise for the intended optical system. Threshold current is typically 25 mA and no more than 40 mA, but the operating point for 60 mW must be established within the stated current limit. Pins 3, 11 and 13 form the DC bias and common connections, while pin 12 provides the laser modulation connection. The monitor photodiode is available separately on pins 4 and 5 for power-feedback circuitry. As no start-up sequence or protection timing is defined, the driver design should include controlled current ramping, reverse-voltage protection and fault limiting.

No. The ALM938-60 suffix identifies the 60 mW output option, but the ordering code does not encode a specific wavelength. The laser family is identified as 1550 nm, while the electro-optical specifications give an operating wavelength range of 1530–1565 nm at the operating current and temperature. The 60 mW code is therefore insufficient to define a precise optical channel or centre-wavelength tolerance. If the application uses a fixed filter, wavelength-selective modulator, dense channel plan or narrow optical passband, the required wavelength should be confirmed during procurement. The thermal control design should then be matched to the agreed operating point rather than assuming any value within the full range.

Line quality is defined by several complementary parameters rather than linewidth alone. The spectral linewidth is no more than 1 MHz, side-mode suppression is at least 30 dB and typically 45 dB, and internal optical isolation is at least 30 dB and typically 35 dB. Relative intensity noise is limited to −157 dB/Hz over 20–1000 MHz, which is the stated RF noise measurement band. Together, these values support use as an externally modulated source where optical purity, source noise and reflection control affect link behaviour. The complete link budget should still include modulator loss, fibre loss, receiver noise and any return loss outside the laser package.

The module uses a hermetically sealed 14-pin butterfly package with a polarisation-maintaining fibre pigtail. The fibre diameter is 0.9 mm, the pigtail length is at least 1 metre, and the nominal pin lead length is 5 mm from the external package wall. Polarisation extinction ratio is at least 18 dB and typically 20 dB when the electric field is aligned with the slow axis. No optical connector type is defined, so the assembly process should allow for the required splice, termination or connector arrangement. Mechanical clearance, lead forming and thermal contact should be checked against the package drawing before the PCB and enclosure are released.

Protection thresholds should be set below the absolute maximum ratings and coordinated with the normal operating limits. Continuous forward laser current is limited to 500 mA, reverse DC laser voltage to 1 V, and continuous TEC current to ±1.9 A. The monitor photodiode permits up to 10 V reverse bias continuously or 15 V for 60 seconds, while storage temperature extends from −40 to 85 °C. In normal operation, the TEC range is narrower at ±1.2 A and the case temperature must remain between 0 and 65 °C. Current limiting, reverse-polarity protection, temperature shutdown and monitor-diode bias clamping can reduce the risk of overstress during start-up, faults or maintenance.