Ascent Communication Technology

1.25G SFP BX 3155 20 km

Ascent’s SFP BIDI 1.25G 20 km transceiver is a compact and efficient optical interface designed for switches, routers, servers, and other networking equipment. Supporting data rates up to 1.25 Gb/s, the module fully complies with the SFP Multi-Source Agreement (MSA) and enables cost-effective bi-directional transmission over a single strand of single-mode fiber. The module offers flexible control through both a TTL-level TX Disable input and an I²C-based digital management interface, allowing precise monitoring and protection of the optical transmitter. A TX Fault indicator provides early warning of potential laser degradation to help ensure long-term link stability. A dedicated Loss of Signal (LOS) output enhances system reliability by detecting insufficient receiver input or partner-device link issues. All key operational states—LOS, link status, disable control, and fault conditions—are accessible via the integrated digital diagnostic interface, supporting real-time system monitoring and remote management.

· Up to 1.25Gb/s Data Links

· A type:1310nm FP Tx/1550nm Rx

· B type:1550nm DFB Tx/1310nm Rx

· Hot-Pluggable SFP footprint

· Single LC for Bi-directional Transmission

· Built-in digital diagnostic functions

· Up to 20km on 9/125μm SMF

· Single +3.3V Power Supply

· Operating Temperature:

Standard: 0°C to +70°C

Industrial: -40°C to +85°C

· Very low EMI and excellent ESD protection

· RoHS compliant and Lead Free

Absolute Maximum Ratings

Parameter Operating Case Temperature	Symbol T_op	Min. 0	Typ.	Max. +70	Unit °C	Note Commercial
		-40		+85	°C	Industrial
Power Supply Voltage	Vcct, R	-0.5		4	V
Relative Humidity	RH	0		85	%

Optical Characteristics(TOP = Tc, V_CC = 3.135 to 3.465 Volts)

Parameter	Symbol	Min.	Typ.	Max.	Unit	Note
Transmitter
Center Wavelength	λc	1290	1310	1330	nm	SFP-LP-3155-20 1
						SFP-LP-3155-20A 1
	λc	1530	1550	1570	nm	SFP-LP-5531-20 1
						SFP-LP-5531-20A 1
Spectral Width	σ			3	nm
Optical Output Power	Pout	-9		-3	dBm	2
Optical Rise/Fall Time	tr / tf			160	ps	3
Extinction Ratio	ER	9			dB
Deterministic Jitter Contribution	TXΔDJ			56.5	ps	4
Total Jitter Contribution	TXΔTJ			119	ps	3
Eye Mask for Optical Output	Compliant with Eye Mask Defined in IEEE 802.3 standard
Relative Intensity Noise	RIN			-120	dB/Hz
Receiver
Optical Input Wavelength	λc	1530	1550	1570	nm	SFP-LP-3155-20
						SFP-LP-3155-20A
	λc	1290	1310	1330	nm	SFP-LP-5531-20
						SFP-LP-5531-20A
Receiver Overload	Pol	-3			dBm	5.6
RX Sensitivity	Sen			-22	dBm	5.6
RX_LOS Assert	LOS_A	-38			dBm
RX_LOS Deassert	LOS_D			-23	dBm
RX_LOS Hysteresis	LOS_H	0.5			dB
General Characteristics
Data Rate
Data Rate	BR		1.25		Gbps
Bit Error Rate	BER			10^-12
Max. Supported Link Length on 9/125μm SMF@1.25G	LMAX		20		km	7
Total System Budget	LB	14			dB	8

Notes:

1. The optical power is launched into SMF.

2. 20 to 80%.

3. Contributed total jitter is calculated from DJ and RJ measurements using TJ = RJ + DJ. Contributed RJ is calculated for 1x10^-12 BER by multiplying the RMS jitter (measured on a single rise or fall edge) from the oscilloscope by 14. Per FC-PI, the actual contributed RJ is allowed to increase above its limit if the actual contributed DJ decreases below its limits, as long as the component output DJ and TJ remain within their specified FC-PI maximum limits with the worst case specified component jitter input.

4. Measured with PRBS 2^7-1 at 10^-12 BER.

Electrical Characteristics (TOP = Tc, Vcc = 3.135 to 3.465 Volts)

Parameter	Symbol	Min.	Typ.	Max.	Unit	Notes
Supply Voltage	V_cc	3.14	3.30	3.47	V
Supply Current	I_cc			300	mA
Inrush Current	I_surge			Icc+30	mA
Maximum Power	P_max			1.0	mW
Transmitter
Input Differential Impedance	R_in	90	100	110
Single Ended Data Input Swing	V_in,PP	200		1200	mVp-p
Transmit Disable Voltage	VD	Vcc - 1.3		Vcc	V	2
Transmit Enable Voltage	VEN	Vee		Vee+ 0.8	V
Transmit Disable Assert Time	T_dessert			10	us
Receiver
Single Ended Data Output Swing	V_out,_pp	300		80	mv	3
Data Output Rise Time	tr			150	ps	4
Data Output Fall Time	tf			150	ps	4
LOS Fault	V_losfault	V_cc – 0.5		V_{CC_host}	V	5
LOS Fault	V_{los norm}	V_ee		V_ee+0.5	V	5
Power Supply Rejection	PSR	100		0.5	mVpp	6
Deterministic Jitter Contribution	RXΔDJ			51.7	ps	7
Total Jitter Contribution	RXΔTJ			122.4	ps

Notes:

1. AC coupled.

2. Or open circuit.

3. Into 100 ohm differential termination.

4. LOS is LVTTL. Logic 0 indicates normal operation; logic 1 indicates no signal detected.

5. All transceiver specifications are compliant with a power supply sinusoidal modulation of 20Hz to 1.5MHz up to specified value applied through the power supply filtering network shown on page23 of the Small Form-factor Pluggable (SFP) Transceiver Multi-Source Agreement (MSA), September 14, 2000.

6. Measured with DJ-free data input signal. In actual application, output DJ will be the sum of input DJ and . DJ.